This volume presents a series of lectures on psychology delivered by Wilhelm Wundt, a figure widely regarded as one of the founding fathers of modern experimental psychology. The work is structured as a course of instruction, moving systematically through the fundamental problems of psychological science as they were understood in the late nineteenth and early twentieth centuries. The lectures range across both human and animal experience, examining the physiological bases of sensation, the psychological construction of perception, and the nature of feeling and will.
The book is notable for its attempt to establish psychology as a rigorous experimental science while acknowledging the philosophical questions that inevitably arise in studying the mind. Wundt draws extensively on laboratory research, including experiments on sensory discrimination, visual perception, and reaction times, but he also engages with broader theoretical questions about the relationship between mind and body, the nature of consciousness, and the development of mental life from its simplest elements to its most complex products.
The lectures are addressed to a general audience of students and educated readers rather than exclusively to specialists. Wundt explains experimental procedures and theoretical positions with considerable care, often walking through the logic of an argument step by step before drawing conclusions. The tone is that of a teacher who wishes not merely to convey facts but to cultivate habits of rigorous thinking about psychological questions.
The work reflects a particular moment in the history of psychology, when the discipline was separating itself from philosophy and establishing its own methods and subject matter. Wundt’s approach is characterized by a commitment to experimental methods where they are applicable, combined with an openness to introspective evidence and a willingness to speculate about the deeper principles underlying mental life. The book thus stands as both a summary of research findings and a statement of theoretical positions that would prove enormously influential in the development of scientific psychology.
Context
Wundt’s lectures emerge from a period of intense intellectual ferment in European science and philosophy. The nineteenth century had witnessed extraordinary advances in physiology, particularly in understanding the senses. Researchers had mapped the anatomy of the eye and ear, measured the speed of neural transmission, and begun to explore the relationship between physical stimulation and sensory experience. The discovery that sensory discrimination follows regular laws—most notably the principle that the just noticeable difference between two stimuli bears a constant ratio to the magnitude of the original stimulus—suggested that mental phenomena might be amenable to mathematical treatment.
This work also appears against the backdrop of longstanding philosophical debates about the nature of perception and knowledge. Empiricist philosophers had argued that all knowledge derives from experience, with complex ideas built up from simple sensations through processes of association. Nativist thinkers, by contrast, maintained that certain fundamental structures of experience, particularly space and time, are innate rather than acquired. Wundt engages directly with these debates, offering psychological evidence and arguments that bear on questions philosophers had previously addressed through speculation alone.
The development of experimental psychology was closely tied to advances in physics and physiology. The wave theory of light, the understanding of sound as vibration, and the discovery of electrical phenomena all provided tools for investigating sensory processes. Wundt’s lectures reflect this interdisciplinary context, moving freely between physical accounts of stimuli and psychological accounts of experience. The work also engages with evolutionary thinking, particularly in discussions of the development of sensory and motor capacities and the comparison between human and animal psychology.
Wundt’s own institutional position was significant. He established one of the first laboratories dedicated to experimental psychology at Leipzig, and his lectures attracted students from across Europe and America who would carry his methods and ideas to their own countries. This volume represents not merely a personal statement but the codification of a new scientific discipline, with its own problems, methods, and standards of evidence.
The period also saw intense interest in the relationship between mind and body. Advances in neurology had demonstrated that specific mental functions could be localized in particular brain regions, while the discovery of reflexes suggested that much behavior could be explained without invoking conscious intention. Wundt’s lectures navigate between materialism and dualism, insisting on the reality of conscious experience while acknowledging the dependence of mental life on physiological processes.
Structure of the Book
The lectures are organized as a progressive course of study, beginning with the simplest elements of mental life and gradually building toward more complex phenomena. The opening lectures address the fundamental problem of measuring sensation. Wundt introduces Weber’s law—the principle that a stimulus must increase by a constant ratio to produce a just noticeable change in sensation—and explores its implications for understanding the relationship between physical stimulation and conscious experience. He discusses the methods by which sensation magnitudes can be measured, the conditions under which Weber’s law holds, and the deviations that occur at the limits of sensory capacity.
From this foundation, the lectures move to a detailed examination of the individual senses. The treatment of hearing considers the nature of tone perception, the phenomenon of overtones, and the distinction between simple tones and compound clangs. Wundt explains how the physical characteristics of sound waves relate to psychological qualities of pitch and timbre, and he discusses the conditions under which tones combine harmoniously or produce dissonance. The treatment of vision is even more extensive, covering the analysis of white light into spectral colors, the theories of color vision, and the phenomena of after-images and contrast.
The middle lectures address the construction of spatial perception. Wundt argues against nativist accounts that treat space as an innate structure of experience, proposing instead that spatial ideas are built up through the association of local signs with movement sensations. He presents experimental evidence, including studies of visual illusions and stereoscopic vision, to support this constructive account. The discussion extends to the perception of depth, the role of binocular disparity, and the psychological processes by which the two eyes’ separate images are fused into a single spatial world.
The lectures then turn to the phenomena of reflex movement and the development of purposive behavior. Wundt explains how initially irregular responses to stimulation become organized and directed through processes of association and learning. He introduces the concept of muscle sensations and discusses their role in guiding movement and in providing information about the position and state of the body.
The final lectures address the feelings and their relationship to sensation and will. Wundt argues that feeling is not a separate faculty but an integral element of all conscious experience, present from the earliest stages of mental life. He discusses the affective tone of sensations, the distinction between sense feelings and more complex emotions, and the ways in which feelings motivate action and give mental life its individual character.
Main Arguments
The central argument running through these lectures concerns the possibility of a scientific psychology. Wundt maintains that mental phenomena can be studied experimentally and that regular laws govern the relationship between physical stimulation and conscious experience. The discovery of Weber’s law provides a model for this enterprise, demonstrating that even the apparently subjective realm of sensation magnitude is subject to quantitative treatment. Wundt argues that the methods of measurement developed for pressure sensations can be extended to other senses and that the same fundamental principles apply across different sensory modalities.
A second major argument concerns the constructive nature of perception. Wundt rejects the view that spatial perception is innate or that sensations themselves possess spatial properties. Instead, he argues that space is a mental product, built up through the association of local signs with movement sensations. The eye learns to interpret the qualitative differences among retinal sensations as indications of spatial position, and movement sensations provide the measure of distance. This constructive account is supported by evidence from visual illusions, experiments on sensory discrimination, and observations of individuals who have recovered sight after congenital blindness.
Wundt also argues for the continuity between simple and complex mental phenomena. The same principles of association and combination that explain the construction of spatial perception also explain the fusion of the two eyes’ images in stereoscopic vision, the development of reflex movements into purposive behavior, and the emergence of complex feelings from simple sense experiences. Mental life is not composed of discrete faculties but represents a continuous development from elementary sensations to the most sophisticated products of thought and imagination.
A further argument concerns the relationship between sensation and feeling. Wundt maintains that feeling is not an addition to sensation but an integral element of it. Every sensation has an affective tone, a quality of pleasantness or unpleasantness that is part of the experience itself. This position opposes both intellectualist accounts that treat feeling as a judgment about sensation and faculty psychology that separates feeling from cognition. Wundt argues that the distinction between sensation and feeling arises only through analysis, after the subject has learned to separate objective from subjective aspects of experience.
The lectures also argue for the importance of physiological explanation in psychology. Wundt insists that psychological processes are dependent on bodily processes and that understanding this dependence is essential for a complete science of mind. However, he resists reductionism, maintaining that psychological phenomena require psychological concepts and methods. The relationship between mind and body is one of interdependence rather than identity, and the task of psychology is to describe mental phenomena in their own terms while acknowledging their physiological conditions.
Key Concepts
Weber’s law stands as a foundational concept in Wundt’s treatment of sensation. The principle states that a stimulus must increase by a constant ratio to produce a just noticeable change in sensation. For pressure sensations, the external pressure must increase by one third of its intensity to produce a just noticeable increase. This law provides a method for measuring sensation magnitudes, treating the just noticeable increment as a unit of sensation. Wundt develops a graphical representation of the law, showing how sensation increases as a function of stimulus magnitude, and he discusses the conditions under which the law holds and the deviations that occur at the upper and lower limits of sensory capacity.
The concept of local signs is central to Wundt’s account of spatial perception. Following Lotze, Wundt uses this term to refer to any constituent of sensation that influences spatial ideation. Each point on the retina and skin has a characteristic local quality, a way of feeling that differs from the qualities of neighboring points. These local signs provide the material from which spatial ideas are constructed through association with movement sensations. Wundt distinguishes between simple and complex local signs, arguing that spatial perception requires the combination of intensively graduated movement sensations with qualitatively graduated local signs of the sensory surface.
Muscle sensations play a crucial role in Wundt’s account of perception and action. These sensations arise from the contraction of muscles and provide information about the position and movement of the body. Wundt argues that movement sensations provide the measure of spatial distance, allowing the mind to estimate how far the eye has moved or how far apart two points on the skin are. The concept also explains various illusions and pathological phenomena, including the experiences of patients with partial paralysis who feel greater effort despite performing the same work.
Sensation fusion refers to the process by which simple sensations combine into unitary ideas. Wundt introduces this concept to explain why a clang is heard as a single tone despite containing many overtones, and why the two eyes’ separate images are fused into a single spatial perception. Fusion is facilitated by harmonious relationships among the elements, such as simple ratios between vibration rates, and it represents a fundamental principle of mental combination.
Contrast phenomena reveal the relativity of sensation. Wundt formulates a general law of relativity: wherever quantitative apprehension of sensations occurs, the individual sensation is estimated by its relation to other sensations of the same sense modality. This principle explains why grey paper appears greenish on a red background, why a moonlight scene can appear brighter than a daylight scene in a painting, and why the same stimulus can produce different sensations depending on its context.
After-images demonstrate that sensory processes outlast their stimuli. Wundt distinguishes between positive after-images, which resemble the original object, and negative after-images, which show complementary colors. These phenomena reveal the chemical nature of retinal processes and provide evidence for the exhaustion and recovery of sensory mechanisms.
Reflex movements represent the simplest form of behavioral response, in which nervous excitation transfers from sensory to motor fibers. Wundt argues that reflexes provide the foundation for purposive behavior, which develops as initially irregular movements become organized through association and learning.
Themes
A recurring theme in these lectures is the relationship between the subjective and objective aspects of experience. Wundt insists that sensations are subjective states that we nevertheless refer to objective causes. The construction of an objective world requires learning to distinguish those features of sensation that reflect the properties of external objects from those that reflect the condition of the sense organ. This distinction is not given in experience but is built up through the association of sensations with movements and the comparison of impressions across different sensory modalities.
The theme of development appears in several forms. Wundt discusses the development of the individual, as when he describes how a child learns to direct the eye toward objects and to perceive spatial depth. He also discusses the development of the species, as when he compares the senses of lower and higher organisms or considers the evolutionary significance of the chemical and mechanical senses. Throughout, he emphasizes that mental capacities that appear innate may actually be the products of gradual development, and that structures which are necessary for the formation of perceptions may not be necessary for their continued operation.
The unity of mental life is another persistent theme. Wundt resists the fragmentation of mind into separate faculties or independent processes. Sensation and feeling are not distinct kinds of experience but aspects of a single conscious state. Perception and movement are not separate functions but intimately connected through the role of muscle sensations in spatial apprehension. The two eyes do not function as independent organs but combine their separate perceptions into a single visual world. This emphasis on unity reflects Wundt’s conviction that psychology must study mental life as it is actually experienced rather than as it appears through the abstractions of analysis.
The theme of measurement and law runs throughout the lectures. Wundt is concerned to show that psychological phenomena are subject to regularities that can be expressed mathematically. Weber’s law provides the paradigm, but similar principles appear in other domains: the just noticeable difference between line lengths is a constant fraction of the total distance, the just perceptible movement of the eyeball is a constant angular measure, and the relationship between pitch and vibration rate follows a regular pattern. These regularities suggest that psychology can aspire to the status of a science, discovering laws that are as precise as those of physics.
The relationship between mind and body appears as a theme in discussions of the physiological conditions of mental life. Wundt acknowledges that mental processes depend on bodily processes, but he resists the conclusion that psychology can be reduced to physiology. The laws of sensation are psychological laws, even though they are conditioned by physiological mechanisms. This position reflects a broader philosophical commitment to the reality of conscious experience and the irreducibility of mental phenomena.
The Author’s Conclusions
Wundt concludes that psychology can be established as an experimental science with its own methods and laws. The measurement of sensation, the analysis of perception, and the study of feeling all reveal regularities that can be investigated through controlled observation and experiment. Weber’s law demonstrates that even the most elementary aspects of conscious experience are subject to quantitative treatment, and similar principles extend to more complex phenomena.
The investigation of the senses reveals fundamental differences in their modes of operation. Hearing and touch are mechanical senses, in which stimulation consists of physical vibrations that set up corresponding motions in sensory structures. Sight, taste, and smell are chemical senses, in which stimulation involves chemical processes that require time to complete. These differences explain the contrasting phenomena of after-effects: auditory sensations cease almost immediately when stimulation ends, while visual sensations persist and undergo characteristic changes.
Wundt concludes that spatial perception is a mental construction rather than an innate structure of experience. The perception of space arises through the association of local signs with movement sensations, and it can be explained psychologically without recourse to nativist assumptions. The same principles of association explain stereoscopic vision, the perception of depth, and the development of purposive movement.
The study of reflex movements reveals that purposive behavior develops from initially irregular responses through processes of association. The eye learns to direct itself toward objects of interest, the hand learns to discriminate spatial relations, and the organism as a whole learns to coordinate its movements in pursuit of its ends. These developments depend on the association of sensations with movements and on the accumulation of experience.
Wundt concludes that feeling is an integral element of all conscious experience rather than a separate faculty. Every sensation has an affective tone, and the distinction between sensation and feeling arises only through analysis. The feelings provide the motivational basis for action and give mental life its individual character.
The final conclusion concerns the relationship between psychology and physiology. Wundt maintains that psychological phenomena require psychological explanation, even though they are conditioned by physiological processes. The laws of mental life cannot be derived from the laws of bodily processes, and psychology must develop its own concepts and methods. At the same time, psychology must remain in close contact with physiology, since the dependence of mind on body is a fundamental fact of experience.
Significance
This work represents a landmark in the establishment of psychology as an experimental science. Wundt’s lectures demonstrate that mental phenomena can be investigated through controlled observation and experiment, and they provide models for how such investigation might proceed. The treatment of Weber’s law shows how psychological regularities can be expressed mathematically, while the analysis of spatial perception shows how complex mental products can be explained through the combination of simpler elements.
The lectures also represent a significant contribution to theoretical psychology. Wundt’s constructive account of spatial perception challenged nativist assumptions and provided an alternative that could be tested experimentally. His treatment of sensation and feeling offered a way of understanding the relationship between cognition and emotion that avoided both intellectualism and faculty psychology. His insistence on the irreducibility of psychological phenomena while acknowledging their physiological conditions provided a middle path between materialism and dualism.
The work had considerable influence on the development of psychology in Europe and America. Wundt’s laboratory at Leipzig attracted students who carried his methods and ideas to their own institutions, and his lectures provided a model for the teaching of scientific psychology. The emphasis on experiment, the concern with measurement, and the commitment to explaining mental phenomena through their elements all became characteristic features of the new discipline.
The lectures also engage with questions that remain central to psychology and philosophy. The relationship between mind and body, the nature of perception, the role of experience in development, and the possibility of measuring mental phenomena are all issues that continue to occupy researchers. Wundt’s treatments of these questions are historically significant not merely as documents of an earlier stage of science but as contributions to debates that remain alive.
The work stands as a monument to a particular conception of psychology, one that combines experimental rigor with philosophical reflection and that insists on the reality and importance of conscious experience. Wundt’s psychology is neither a pure science of behavior nor a branch of philosophy but an attempt to study mental life through methods appropriate to its subject matter. This conception continues to inform debates about the nature and methods of psychology, and the lectures remain valuable reading for anyone interested in the foundations of the discipline.
Inside the Book
The Scope of Weber’s Law
The discussion opens by questioning whether Weber’s law governs all quantitative judgments of sensation or only a narrow range of cases. The text argues that measuring the just noticeable difference is actually a special instance of a broader relationship of dependency between sensation and stimulus. One can move gradually from barely perceptible increases to much larger ones: if a sensation grows by a just noticeable amount, and then that new sensation grows again by another just noticeable increment, the gap between the first and third sensations becomes clearer than between the first and second. Repeating this process builds toward far greater intensity. But leaping directly from a weak to a strong stimulus yields no precise information about the underlying dependency. The analogy offered is counting grains of wheat in a heap—one must count each grain individually rather than estimate the whole. Sensations, therefore, must be broken down into elements equivalent to just noticeable differences.
This method compares one sensation with another at a time, but once a unit is fixed, other sensations can be measured against it. For pressure-sensations, the unit is the sensation from a pressure of one gramme, and the relation is expressed by the fraction one-third: the external pressure must increase by a third of its intensity to produce a just noticeable increase. Thus one can distinguish one and one-third grammes from one gramme, and two and two-thirds from three, and so on. If all equally noticeable increments are treated as equal magnitudes, then the just noticeable increase from one gramme equals that from ten grammes. Any sensation can be thought of as composed of a number of such increments, beginning where the stimulus first excites a sensation. A sensation is twice or three times as intensive as another when it contains twice or three times as many equal increments. This system presupposes following sensation in its gradual increase, just as all measurement does, with the just noticeable increment serving as the unit—analogous to measuring a scale in inches.
The method would be cumbersome, but Weber’s law permits quicker prediction. For pressure-sensations, the sensation from one gramme must be intensified by one-third of a gramme to increase by one unit. To find the pressure increase for a six-unit increase, the text describes a scale beginning at a zero-point of one gramme, with perpendiculars drawn to represent stimulus magnitudes. Each perpendicular is lengthened by one-third of the previous one, and connecting their upper ends yields a curved line ascending more steeply at higher values. This curve shows the dependency of sensation on stimuli for all points, including those between units. A sensation-difference corresponding to a point between unit values is not perceptible, but it would be wrong to conclude it has no existence—perceptible differences are reached by accumulating imperceptible ones. It is merely chance that just noticeable differences fall at points one, two, three; if the initial weight were different, the scale would shift but the law would remain. Measurement is discrete, but the scale is continuous: just as weights smaller than one-thousandth of a gramme exist, so do sensation-differences we cannot cognize.
The scale as described is not perfectly suited to its purpose, since it starts from a stimulus-unit rather than a sensation-unit. The true zero-point should be where sensation begins, which is not the zero-point of the stimulus. Stimuli must attain a definite magnitude to be sensed, determined by the sense organ. If one-third of a gramme is the magnitude for a just noticeable pressure-sensation, this is represented by a perpendicular at the zero-point, and the same relative increases follow as before, but with the new vertical standing for one-third of a gramme rather than one gramme. Two measurements suffice for any sense-department: the constant relation of sensation-intensity variation with stimulus-intensity, and the measurement of the just noticeable sensation. The first divides the sensation-scale; the second gives its zero-point. For pressure-sensations, with a constant ratio of one-third and a just noticeable sensation from one-third of a gramme, any problem can be solved. For a sensation from one gramme of pressure, starting at zero, each unit increases by one-third, yielding nearly fourteen units for one gramme. If sensation increased directly as stimulus, fourteen units would correspond to an increase of not quite five grammes, but they actually require an increase of almost a whole gramme.
The Just Noticeable Sensation in Sight and Hearing
The conditions for determining the just noticeable sensation differ between sight and hearing. For the ear, a state of absolute inactivity—silence—is realizable, allowing a clear distinction between noise and silence. Visual darkness, however, is not equivalent to auditory silence. Diminishing external light or closing the eyes does not produce a complete absence of light-sensations. External light penetrates the closed eye, and the pressure of closing the eye itself acts as a retinal stimulus, producing a light-sensation. Stronger pressure intensifies this shimmer until the field of vision floods with light. Even without mechanical stimulus, in the darkest night, the eye is never free from light-stimulation. One can observe darkness deepening and lifting, with blurred outlines and flashes of lightning—not external light, since this accompanies movement and persists in complete isolation. The deepest black we can see is a light-sensation; the darkened field of vision has the same form as the bright field. Objects outside this field are not seen as black but not seen at all. The blackest black is therefore the weakest sensation of light, not the absence of sensation. There are degrees of darkness, allowing gradual passage from deepest black to brighter, to grey, and finally to white.
The ancient view that the eye is a source of light has some foundation, but this internal light cannot be used to see external objects. The light-sensation in the dark is caused by a stimulus within the eye, whereas seeing objects requires the light-stimulus to proceed from them. This continual excitation is intelligible because the eye is the most sensitive sense-organ. Normal physiological conditions, such as chemical processes of nutrition, may stimulate the neural epithelium. Muscles moving the eyeball also exert pressure, a stimulus always operative even in rest and increasing during movement, intensifying light-sensations in the dark. These conditions prevent measuring the stimulus magnitude for a just noticeable light-sensation. The eye always has a sensation more than just noticeable. We can only determine the least light-intensity that is just noticeably brighter than the black of the field of vision in absolute darkness, done by passing a constant current through a metal wire until it becomes luminous. The just noticeable intensity of light is approximately one-three-hundredth of the light of the full moon reflected from white paper. Units of sensation and stimulus have been determined for pressure, sound, and light, but not for taste, smell, and temperature, due to the inability to control stimuli and the impossibility of a zero-point of stimulation.
Upper and Lower Limits of Weber’s Law
A question arises: do the just noticeable stimulus-difference and stimulus-magnitude stand in a definite relation? If sensibility varies, does sensibility to stimulus-difference also vary? The law states a stimulus must always increase in the same ratio to condition a definite sensation-difference. If sensibility is reduced by half, twice the stimulus is needed for a noticeable sensation, but the relative increase required remains the same. This hypothesis is confirmed by observation: if sensibility changes, every stimulus is sensed more or less intensely, but the difference between two stimuli remains the same in sensation. Sensibility to stimulation does not affect the law of dependency of sensation upon stimulus. The investigation concerns the dependency of sensation upon internal stimulus operative in a sensory centre of the brain, but began with external stimulus.
After-Images and Sensory After-Effects
The discussion opens by contrasting the behavior of hearing and sight once a stimulus ceases. Tone-sensations vanish almost instantly when the sound stops, leaving no perceptible trace. Visual sensations, however, persist noticeably. A red-hot ember swung in a circle appears as a complete ring of fire, proving the light-impression lingers in the eye for the duration of its path. If one fixates a luminous object and then closes the eyes, an after-image appears on the dark field. This image first resembles the object exactly—the positive stage—then fades, and finally reverses into its opposite: white becomes black, black becomes white, and colours transform into their complements, so a red object yields a greenish image. This later phase is the negative or complementary after-image, observable even with open eyes when staring at an intensely bright source like the setting sun and then looking at a roadway.
These phenomena demonstrate that the retinal stimulation-process outlasts the external stimulus by several seconds, with the direct continuation followed by an opposite condition of the sense-organ. The complementary effect is explained by partial retinal exhaustion: if the retina’s sensibility to red is depleted at a given spot, white light appears there as though no red rays affected it, and since subtracting red from white yields green, a red object leaves a greenish trace. Contrast with the background can intensify these complementary images.
The differing after-effects point to fundamentally different excitation processes. Sound vibrations likely set up corresponding vibrations in the cochlear membrane where auditory nerve fibres terminate, with individual fibres tuned to various tones—a mechanical process that ceases when vibration stops, aided by damper-like structures. Light-stimulation, by contrast, appears photochemical. The retina resembles a photographer’s prepared plate: deep red in darkness, it bleaches and turns white when exposed. Chemical processes require more time than simple motion transmission, explaining the positive after-image as the duration of chemical decomposition and the negative as an exhaustion effect. Sight and hearing thus represent two fundamental forms of sensory excitation—chemical and mechanical—referring not to processes within the nerves themselves but to how external stimuli affect nervous terminations. The mechanical senses include hearing and cutaneous pressure; the chemical include sight, temperature-sense, smell, and taste. Touch, the earliest sense-organ in low organic life, may hold significance for physiological developmental history by encompassing both types.
Phenomena of Contrast
Many changes in light and colour sensation cannot be explained by after-effects or exhaustion alone. When light passes through red glass and casts a shadow on the red-illuminated surface, the shadow—objectively containing only diffused white light—appears green rather than grey. This occurs naturally in tree shadows when the setting sun is reddish. Experiments confirm the effect: rotating colour tops with coloured sectors on white backgrounds produce grey rings that appear complementarily coloured to their backgrounds. Grey paper laid on coloured backgrounds takes on complementary colours—grey on red appears greenish, on green reddish, on yellow bluish, on blue yellowish. Grey squares on black and white backgrounds respectively appear almost white and approaching black. Surface extent matters: very large shadows appear grey at their centre, with colour appearing only at edges. These phenomena receive the general name “contrast phenomena,” and “contrast colour” and “complementary colour” may be used synonymously.
Some physiologists explain contrast by diffusion of excitation over surrounding retinal regions, analogous to after-images. This analogy fails for three reasons: after-images have positive and negative phases while contrast is always negative; after-images require time to develop while contrast is instantaneous; and stronger stimuli should produce stronger diffusion effects, yet weak stimuli can produce stronger contrast than strong ones. An alternative “judgment theory” holds that contrast depends on deception of judgment—we judge colours relative to our assumption that diffuse daylight is white. The author objects: we clearly perceive reddish illumination from the setting sun as coloured, not white; the theory requires extraordinarily complicated unconscious inferences; and experiments excluding mediating influences still show contrast effects.
Contrast phenomena reduce to sensational relativity, already familiar from Weber’s law. The author formulates the general law of relativity: wherever quantitative apprehension of sensations occurs—whether intensity or quality—the individual sensation is estimated by its relation to other sensations of the same sense-modality. This estimation may involve preceding and following impressions, simultaneous impressions, or only simultaneous impressions. The law has predominantly psychological significance: we never apprehend mental state intensity in isolation but through direct comparison of conscious states, and it likely extends to every case where mental process intensity is quantitatively apprehended.
Reflex Movements and Their Development
Sensation leads to muscular movement when sufficiently intense and uninhibited. Such movements are termed reflex movements—nervous excitation transfers within central organs from sensory to motor fibres, with the stimulus “thrown back” or reflected. Reflexes require only that sensory nerves retain connection with central organs and that these connect via motor nerves to muscles. Light-stimuli initially excite only irregular movements; over time these become definite and purposive—the eye moves to bring the light’s image onto the yellow spot, and when a light moves to and fro, the eye follows continuously.
The determinate relation of the yellow spot to reflex movements cannot be innate in nervous interconnection; if it were, the first ray on the retina would release the same reflex later observed. The force transmitted from sensory to motor fibres depends on stimulus intensity and the temporary condition of transmitting organs; nothing explains why a strong stimulus near the yellow spot should produce slight movement while a weak peripheral stimulus produces extensive movement. Influences must operate during sense-development so that the reflex’s extent and direction depend on the place stimulated, while greater sensitivity shows only in greater energy and rapidity.
The skin over the entire body is sensitive, as is the whole retina except the optic nerve’s entry point. Touching different skin regions yields clearly different sensations, and even corresponding places on the two body-halves differ slightly. In the retina, fixating red paper and moving it laterally shows the colour gradually darkening, taking a bluish tinge, then passing to pure black—for any colour or white. This change occurs in all directions but with different rapidity: outward or upward movement passes through colour-tones faster than inward or downward. We do not notice these peripheral colour changes because a sensation is not determinate and invariable but the product of associative relation to other sensations. Colour-contrast phenomena show co-operative determinants can make us see blue red and red blue; similarly they can prevent noticing peripheral colour differences. Sensations from ordinary contemplation of large uniform surfaces are entirely uniform: fixating different portions successively on the yellow spot gives the same colour-impression. Original sensation-differences have been eliminated through thousands of experiences by referring them to spatial distribution of impressions, “with the certainty and precision of a machine.”
The universal rule of sense-perception is that we neglect sensation-characteristics not directly connected with objective contents of perception. Sensation-differences across skin and retina regions are likely far greater than experiments show; only when extraordinarily large are they apprehended as subjective. The cause of local sensation-differences is entirely local, found in sense-organ structure—s lighter variations in retinal end-organs. Sensitivity to red decreases toward the retinal periphery; ordinary red-blindness may be an extension of normal lateral-retina sensibility to the centre. In skin, bulb-shaped end-organs are distributed in varying quantities, with differences in epidermis thickness and nerve-supply also mattering.
Each sensation is recognised by its dependence on the place of impression; locality is recognised through definite sensation-characteristics depending solely on that locality. This is the first condition for reflex regularity—found in organ structure.
Stereoscopic Vision and Depth Perception
The discussion of binocular vision begins with the fundamental fact that the right and left eyes each see slightly different aspects of a three-dimensional object, with each eye perceiving portions invisible to the other. Using the example of a truncated cone, the image seen by the left eye differs from that seen by the right, and neither drawing alone suggests depth. Only when the left-eye image is presented to the left eye and the right-eye image to the right eye does a definite tridimensional impression arise, comparable to viewing the actual object. This requires specific fixation—the left eye must fixate the smaller circle in one drawing, the right eye the smaller circle in the other—which proves difficult because eye movements are normally concurrent, both eyes directed at the same point. This concurrence arises from reflex mechanisms, since distinct points attract the gaze and both eyes follow the same law, making their movements interconnected. Only practice can overcome this impulse to common fixation.
The Stereoscope and Its Fundamental Experiments
To overcome the difficulty of fixation, Wheatstone constructed the stereoscope, with Brewster’s form using two angled prisms that divert the rays from drawings placed behind them so that images fall on corresponding retinal areas even while the eyes fixate a common point. This reproduces the retinal conditions of viewing a real object. Fundamental experiments show that presenting two vertical lines at different distances to each eye yields a common image with one line in the plane of the paper and another behind it, matching normal binocular viewing. Similarly, oblique lines with slightly different inclinations produce depth, with the upper or lower extremity appearing more remote depending on the inclination. These constitute the two fundamental stereoscopic experiments, and curved lines work equally well. Depth never arises from horizontal lines at different distances, since nature never presents such conditions—boundary lines are always vertical or oblique. These facts prove that the eyes perceive independently, combined only secondarily. The theory that the eyes function as one organ, with nerve fibers dividing to corresponding retinal points, is impossible; if true, the cone would appear with non-corresponding parts merely overlapping, and no tridimensional object would emerge. The fusion of separate perceptions must therefore be psychological—an unconscious, involuntary act of sensational association, analogous to constructing a model from projections but occurring without conscious effort.
Association, Movement Sensations, and Local Signs
This fusion rests partly on the constant presentation of corresponding projections, but more strongly on the mental endeavor toward permanent association of simultaneous ideas—the same force operative in areal perception. Movement sensations provide the primary measure of spatial distance. When fixating points on a plane surface, non-fixated points affect approximately coincident retinal positions with similar sensational coloring, while points at different distances fall on non-coincident positions with divergent sensational character, distinguishing surface perception from depth perception. Some authorities claim that only coincident retinal images appear simple and that depth perception consists in neglecting double images, but experiments refute this: lines on differently situated retinal portions fuse into a single depth-perceiving line, while lines on corresponding points appear separately. Depth cannot arise from neglecting double images; rather, it requires clear apprehension and combination of separate perceptions. Depth perception originally arose through successive convergence and divergence movements, yet it can arise with the eye unmoved, as demonstrated by electric spark illumination of stereoscopic pictures, too brief for eye movements yet producing clear tridimensional ideas. Local signs—permanent attributes of retinal sensations—enable the eye to dispense with continuous movement, for differences in local sensation character indicate extension in the third dimension just as similar character indicates extension in a plane.
Combination of Dissimilar Images, Reflection, and Lustre
The fusion of retinal images exemplifies a general ideational law: when irreconcilable impressions are presented, separate simultaneous apprehension is impossible, and either combination occurs or alternate apprehension follows. Circles of nearly equal size fuse into one circle of mean diameter, and horizontal lines with slightly different vertical separation yield lines at mean distance. Entirely different objects, however, produce alternation—first one picture appears, then portions of the other force forward, then the second alone—with no permanent composite forms. Letters like U and W never fuse but alternate with fatigue, while compatible letters unite into a single form, though less steadily than in monocular vision. Reflected images in polished surfaces show unaltered colors despite retinal mixture with the reflecting surface’s color. When a mirrored image falls exactly on a directly seen object, the images fuse and produce color mixture, but boundary lines compel assignment of different distances, enabling separation. Lustre arises from this ideational process.
Phenomena of Suppression in Binocular Vision
A third form of binocular apprehension occurs when one eye’s perception has considerable preponderance over the other due to the nature of external impressions, so that the predominant impression alone becomes an idea while the other is completely ignored. Presenting a white square to one eye and only black to the other produces not a mixture but the idea that both eyes see a white square on black ground, with the white as intensive as seen by the first eye. Similarly, presenting a dark red object on white background to one eye and a dark green object to the other results in only red being seen, while on a black background only green appears, since each color contrasts more strongly with its respective background. On a grey background, both perceptions come to consciousness with approximately equal intensity, producing lustre. Suppression may be restricted to part of an image, especially when one retinal image has much greater extension. These experiments show that binocular perceptions always form a single idea on the analogy of natural vision conditions, through numerous associations acting in harmony or opposition. Suppression and ideational rivalry appear when associations oppose, and the binocular visual idea is a mental resultant of the originally separate perceptions of the two eyes.
The Feelings and Sense-Feelings
Mental phenomena studied thus far—ideas from sensations—serve knowledge of the external world, but minds never apprehend things without joy or sorrow. Feeling and will accompany sensations and ideas, determine actions, and give mental life its individuality. Feeling passes into impulse, impulse into voluntary action, and voluntary action references objects given as ideas. All feelings agree in implying a condition of the feeling subject—an affection or activity of the self—while ideas always have objective reference. Some argue that hunger, pain, and touch are sensations accompanied by nervous processes, while feeling is purely mental, but if we give up reference to subjective pleasure-pain conditions, we have no reason to unite affective states in a common class. One process may be both sensation and feeling, and complex feelings depend upon ideas objectively empty of feeling. Feeling and sensation are not originally distinct: the simple sense-feeling is contained in the sensation, and the ultimate fact is that we sense and feel. The eye and ear require intensive stimulation for strong sense-feelings, but introspection reveals affective tone even in weak visual and auditory sensations. Cutaneous sensations are usually referred to external impressions unless painful, with weak stimuli exciting tickling or itching characterized by diffusion. Smell and taste carry distinct pleasure or unpleasantness even at weak intensities, fused so closely with sensation they seem inseparable, serving as subjective indications of impressions to seek or avoid.
Clearness, Distinctness, and Apperception
Experiments with momentary visual impressions demonstrate that no abrupt transition exists between degrees of ideational clearness—only continuous gradation. Three kinds of ideas appear: clear, more obscure, and quite obscure, differing only in degree. Leibniz’s terms are adopted: the appearance of an obscure idea is “perception,” and the appearance of a clear one is “apperception.” Perceived ideas lie in the field of consciousness, while apperceived ideas sit at its fixation-point.
Lecture XIX: Association of Ideas
Wundt begins by defining “association of ideas” as the interconnections of memory-ideas with sense-perceptions or with other memory-ideas. He notes that the term, originating in English association psychology, is both too narrow and too wide: too narrow because it excludes connections where ideas appear simultaneously as a complex totality, and too wide because it includes both simple recollection and complex logical thought. He will use “associations” only for ideational connections lacking logical-thought characteristics. The doctrine began with observation of idea reproduction, essentially modernizing Aristotle’s psychology of memory. Conscious recollection requires distinguishing inducing from induced ideas, but recognition of an idea as previously experienced need not accompany revival. Memory presupposes association, but not every association involves memory.
Where associated ideas form a simultaneous conscious complex, Wundt calls these “simultaneous associations,” including fusions of simple sensations composing complex sense-perceptions. Eye-movement influences visual-space perception even at rest; one may be deceived about object position through intended-but-unexecuted ocular movement. Interconnections of different senses’ perceptions—seeing an instrument while hearing its clang—he terms “complications” with Herbart. Verbal ideas are the most frequent complications, connecting acoustical impressions with movement-sensations and visual impressions of written characters. Recalling a rose’s scent is usually illusory: one has a visual picture, a nose movement-sensation of inhalation, and touch sensations from actual air intake—the true smell-sensation is absent or faint. Taste memory-images similarly contain little actual taste, represented instead by movement-sensations varying with mimetic expression.
Connections of externally excited sense-perceptions with related memory-images constitute “assimilation.” The memory-image is the “assimilating element”; sense-impression sensations are “assimilated.” The resultant complex idea mixes given impressions with numerous memory-images, inseparable in analysis. Examples include reading over printer’s errors, filling out indistinctly heard lecture sentences, stage scenery appearing as perfect landscape reproduction, and puzzle pictures where once the hidden head is found, it stays. When reproduced elements so predominate that the resultant idea is inadequate to sense-perception, this constitutes illusion. No hard line exists between memory-images and fancy-images; memory-images exactly reproducing previous perceptions “simply do not exist.” Ideas are processes, not permanent objects, and never exactly recur because their conditions never repeat. Assimilation always involves two processes: likeness-connection (sense-impression calls up previous similar sensations) and contiguity-connection (these mediate arousal of other elements connected with them previously). Both processes are present in every concrete association.
Lecture XX: Successive Associations
Speaking of “laws” of association is incorrect—these are forms, not laws, merely classificatory concepts. Aristotle distinguished four memory kinds (similarity, contrast, simultaneity, succession). Modern usage omits “contrast” and unites spatial co-existence with temporal succession under “external contiguity,” reducing to two forms. But the terms wrongly suggest elementary processes rather than classificatory headings of products composed of many simple processes. Each successive association contains a direct connection of like elements plus contiguity-connections of externally contiguous elements. Predominance of like-element connections yields similarity-association; predominance of external connections yields contiguity-association.
Recognition is a simple case of successive association, while cognition is a simultaneous association. Although contiguity-connections are involved in cognition, they remain wholly indefinite, resulting only in a “feeling of cognition”—the object is seen as new but belonging to a known class. The recognition-feeling is akin to the cognition-feeling but differs qualitatively and is generally far more intensive. In mediate recognition, secondary ideas are clearly present in consciousness. For immediate recognition, where auxiliary ideas are not noticeable, Wundt argues they are in consciousness but obscure, citing experiments on degrees of clearness with momentary impressions. The supposition that ideas which have disappeared from consciousness can still exert influence is improbable, as it would commit one to the untenable position that vanished ideas persist unconsciously with the same attributes—making them indestructible objects rather than dispositions towards repetition.
Recognition’s forms present a continuous transition from simultaneous to successive association. Immediate recognition approximates assimilation. If extraneous ideas come to clear consciousness, the simultaneous association passes into succession. When an associatively excited idea is apprehended as previously experienced, the process becomes a successive act of memory. The analysis into temporal series depends on two conditions: one revived idea may enter consciousness later than another, or several revived ideas may appear simultaneously but be successively apperceived. Like elements call up like elements, then others connected with them. The process is shaped by mutual intensification of like and repression of opposing elements. All mental experiences are continuous and interconnected; each point can be excited from any other.
The passage then addresses the apparent “spontaneous origin” of ideas. Experiment gives the key: indirect association. An observer in a dark room is presented with momentary light-stimuli in series, then connected with secondary ideas. When principal terms are presented again without secondary objects, associated ideas from the same series appear. The secondary ideas are seldom clearly remembered; the observer cannot tell why he associates one term to another. The secondary idea was obscurely present and excited the associated term. The only difference from ordinary association is that certain members remain unknown, making the connection appear broken.
All ideational connections take origin from likeness and contiguity, but the inference “all ideational connections are associations” is unjustifiable. Concepts are characteristically different from associations. Seeing a picture of a man involves assimilation and recognition, but none of these gives the concept of man. The conceptual quality cannot be a specific attribute of the idea; the distinguishing mark is the accompanying consciousness that the particular idea has only vicarious value. This is attended by a “conceptual feeling,” consisting in concomitant ideational processes—processes of judgment. Concepts obtain significance only as elements in judgment. The most obvious subjective mark of intellectual process is the accompanying feeling of activity. Intellectual activity falls under the concept of internal voluntary action, or active apperception. A “free” action is not unconditioned but results from the whole previous development of consciousness—the “self.” Associations intrude upon intellectual functions; intellectual connections can enter contiguity-relations and be revived as external association, without the feeling of activity. The first products of intellectual activity are simultaneous aggregate ideas. Their analysis gives rise to trains of thought. Logical thought is governed by a dichotomic law, expressed in grammatical distinctions of subject and predicate.
Mental Derangement and Language Decay
The passage opens with observations on the gradual decay of intellectual functions as manifested in the language of the insane. Written records prove superior to oral speech for this study because the rapid torrent of words accompanying flights of fancy cannot be readily followed. Wundt recounts chancing upon a book “privately printed for the author” in which nearly every stage of disintegration could be traced. Its opening sentences are correct in form and expression, though content shows beginnings of abnormal thought. Then follow, with increasing frequency, descriptions of unmistakable hallucinations and linguistic solecisms, with intrusion of disconnected associations becoming more evident, until finally, on the last few pages, no sentence reaches its correct grammatical conclusion.
Subjecting these phenomena to careful analysis reveals how inexact and superficial it is to speak of them as due to “a lowering of the mental functions.” Regarding flights of fancy, mental functions are rather raised in a particular direction than lowered. The normal mind lacks the abundant supply of associations sometimes met with in mental derangement.
Animal Play and the Limits of Association
Wundt continues his analysis of animal play by emphasizing that mock fighting is the one form that resembles human life relations. He excludes trained animals from consideration, since their performances are not genuine play. Dogs, cats, and monkeys show affection to their young by pretending to fight, and this play indicates high mental development. The crucial point, however, is that animals play, not the nature of the play itself. Only animals capable of reproducing pleasurable experiences in memory and modifying them to retain only pleasant aspects can engage in play. Complex associative and affective activity suffices for playful actions. Animal play shows no inventiveness or orderly working-out of a general idea; only where such exists can play express imagination. Animal play is therefore “purely associational play.” A dog seeing another dog may feel no hostility but has an inclination to exercise strength in mock fight, gaining pleasure from real fights. If this impulse is obeyed in a friendly mood, a mutual trial of strength results, often ending in real battle—as observed in dogs and monkeys. In long-domesticated animals like dogs, inherited instinct appears moderated; the connate fighting impulse becomes a connate impulse to play.
No Concepts, Judgments, or Inferences in Animals
Wundt asserts that animal actions resembling imagination lack purposive comprehensive connection of ideas and inventiveness. Writers on animal psychology err by interpreting simple associative processes as apperceptive intellectual operations. He examines Romanes’ report of an elephant’s intelligence, which claimed elephants possess “abstract ideas.” Even understanding this as general experiential concepts, the facts show only developed associational activity. The elephant lifted various objects—clothes bundles, tree-trunks, heavy metal—gradually “taking in knowledge” of things: light objects thrown easily, heavy ones slowly with muscular preparation, cutting instruments cautiously. The observer concluded elephants recognize hardness, sharpness, and weight. Wundt argues that only associations between visual impressions and tactual properties are needed; such associations would be necessary even with general concepts, but once formed they suffice without concept formation.
Wundt then describes his own experiments with his poodle. He spent much time seeking indications of general experiential concepts in the dog, never demonstrating them. He taught the dog to close a door by pressing with forefeet on command “Shut the door!” The dog learned on one particular door in his study. When asked to repeat on another door in the same room, the dog looked astonished and did nothing. After considerable trouble, the dog repeated the trick under altered circumstances, then obeyed at any similar door. The dog formed no general concept of “door” initially; action depended on individual association. Wundt stood the dog on hind legs against the open door while giving the command until voluntary response occurred. When the dog learned the second door, Wundt rejects concept formation: the specific association between particular door and closure became obscured through repetition at several doors; particular associations developed into “similarity-association.” No indication existed of consciousness that a particular object vicariously represents a whole category—the principal characteristic of concept formation. The dog had only a confused idea of a door’s “nature.” When ordered to shut a door opening outward, the dog made the same movement—opened instead of closed—and could not be brought to do otherwise despite obvious unhappiness. Only after several occasions of being let out and made to shut the door from outside did the dog go out and repeat the attempt from the other side, then scratched for readmission.
Alleged Judgments and Inferences
Alleged judgments and inferences in animals resolve into obvious associations, failing where externally suggested association touches intellection proper. Wundt took his poodle on summer evenings to a garden across a stream accessed by boat. Banks were crowded with boats plying to and fro. One day the poodle stayed behind with other dogs, arrived late, and had to swim—unpleasant since he disliked water. Days later the same misadventure occurred; the dog ran up and down whining. A boat-load of passengers pushed off; he sprang in and crossed dry-footed, thereafter crossing this way frequently. Wundt asks what was in the dog’s mind: did he think “my master has crossed; this boat is about to cross; therefore I shall overtake him”? Translating the action into this reasoning deals not with the mental process but a logical interpretation. The two processes differ characteristically. If the dog had sprung into a boat lying on shore waiting for passengers, the association between boats and passage might have formed through frequent journeys—more complicated, nearer intellectual operations. But the dog never entered an empty boat and waited; only when the boat pushed off did he associate this crossing with previous journeys. The action bears every mark of simple association. If later the dog sprang into empty or filling boats, this is gradual extension of associational series from practice, not sudden logical reflection. Many accounts of animal intelligence would admit similar interpretation if all stages of conduct were known.
Language and Association
Animal “intelligence” manifestations are adequately explained as relatively simple associations; no traces of logical reflection or imaginative activity appear. Animals lack language, the characteristic function of intellectual processes. Animals express emotion; higher ones show limited evidence of idea-emotion connections. But expressive movements never show regular articulation or reflection in organic structure of intellectual ideation. Animals possess elements of language as they possess elements of consciousness serving as bases for intellectual function, but not language itself. Absence of this external mark justifies inferring absence of those mental functions. Physical obstacles don’t prevent animal speech—many animals’ speech organs could clothe thought in words if thought existed. The old answer is correct: animals do not talk because they have nothing to say.
Rhythm and Emotion
Wundt turns to rhythm, which ranks with harmony and disharmony as a psychological motive in musical composition, containing elements of both expectation and satisfaction. Regular repetition in rhythmical sense-excitation makes us expect each succeeding stimulation, with expectation immediately followed by satisfaction. Rhythm never involves strain—if it does, it is simply bad rhythm. In pleasant rhythms, satisfaction follows expectation as quickly as possible. Every impression arouses expectation of another while satisfying the expectation aroused by its predecessor, whose temporal relations it reproduces. Rhythm is thus an emotion compounded of expectation and satisfaction. Broken rhythm is emotionally identical with disappointment.
Hope, Fear, and Related Emotions
Hope and fear are special forms of expectation. Expectation is indefinite, referring to desirable, undesirable, or indifferent events. Hope gives definiteness as expectation of a desirable result; fear as expectation of something undesirable. It is hardly correct to call hope future joy or fear future sorrow—feelings cannot penetrate into the future any more than senses can. Hope and fear are expectation of future joy and sorrow, not joy and sorrow themselves; either may be unrealised. Fear of immediate disagreeableness is called alarm. Fright bears the same relation to alarm as expectation does to surprise—fright is surprise occasioned by sudden terrifying occurrence. It becomes consternation when the occurrence physically paralyses the individual; it is called terror when he stands amazed before the event. Consternation is the more subjective side of fright; terror its objective side. Continued fear becomes uneasiness: the uneasy mind is always afraid, every occurrence alarms it—the emotion has become permanent but less intensive.
Intellectual Feelings
Four kinds of intellectual feelings exist: logical, ethical, religious, and aesthetic. Attaching to complicated ideational connections, they almost invariably pass over into emotions, exerting influence exceeding other affective processes. Wundt discusses logical emotions because they are often overlooked and because their relationship to future emotions illustrates emotion’s passage into intellectual forms.
Character as the Ultimate Cause of Volition
The discussion turns to the question of whether experience can prove that character is solely the product of external influences. The hypothetical case of two men with absolutely identical life courses is deemed unrealizable, so the truth is conjectured to lie between the extremes: character is partly a result of conditions of life and partly an original possession of the personality. However, this does not settle the causality of character, as its uncaused beginnings may still be terms in a more universal causal nexus. Personal character is stated to be the ultimate cause of volition.
This leads to the question of individual responsibility, answerable independently of disputes over free will. Punishment cannot affect the external occasion of a crime but targets the criminal character, acting on its own initiative. This character is placed in a community and finds a foreign causality there. Every society is conceded the inalienable right to defend itself against attacks from its members, as the general will stands above the individual as the individual stands above its own organs.
The Origin of Character’s Germ
The individual brings the germ of future character into the world. Two hypotheses explain this endowment: special creation or a resultant of previous generations’ conditions. The choice depends on one’s metaphysical theory—whether one sees life as original creation or developmental continuity. The earliest developmental stages contain rudiments of all capacities, but their contents cannot be demonstrated with certainty. The inclination to admit no gap in the causal chain connecting individual constitution with the community’s general nature stems from the endeavour for a single theory applicable to individual and social mentality. If character grows from a causal nexus beyond personal existence, volition’s determination is incalculable from influencing factors, tracing ultimately to the causality of the universe. This justifies religion’s symbolic view of will as God’s gift.
Volition vs. Chance
Since character originates in a causal nexus beyond individual life, the innermost causation of volition must remain unknown. This distinguishes volition from chance: chance depends on a defect of knowledge that can possibly be remedied, while volition depends on a necessary, irremediable defect. Chance occurrences appear as apparent exceptions to causal law, but volition seems an actual exception. The more character is determined by personal experience, the greater the confidence in predicting its actions; as will matures, its direction becomes more certain.
Concluding Remarks and Immortality
The lectures declined to base considerations on a fixed conception of mind, instead acquainting with facts through introspection, experimentation, and observation. At the end, the question of ultimate psychological questions is raised. One problem is excluded as insoluble: the mind’s condition before or after conscious life, which transcends empirical doctrine and scientific knowledge, like the ‘creation’ of the world in physics. The hope of constructing knowledge of supersensuous objects has proved a fatal illusion. The question of immortality, a principal problem of metaphysical psychology, necessitated emphasizing the mind’s substantial simplicity, leading to the Herbartian metaphysic’s logical extreme—a mental atom of simple quality with unalterable content, comparable to a simple sensational quality like ‘blue’ or ‘red.’ Empirical psychology aims only to explain the interconnection of mental phenomena and declines to furnish information on supersensuous mental existence. Philosophy, however, may pass beyond facts to a coherent theory of the universe, supplementing experience by continuing developmental series on the same lines beyond experience’s bounds. The individual stands at the centre of mental developments, contributing to the achievements of the human mind. If mental development ended in nothingness, the whole mental content of the universe would lose significance. This philosophical notion of purposiveness gave rise to the idea of immortality, though mankind transformed this general conviction into belief in each individual mind’s imperishability with its sensuous contents. Psychology proves sense-perceptions and memorial images depend on bodily functioning; a continuance of sensuous consciousness seems irreconcilable with experience. But the idea of immortality in its true philosophic foundation—mental development as a constituent of universal mind—has nothing urged against it by empirical psychology.
Psychophysical Parallelism
Two further questions require answers: the relation of mental to bodily processes and the nature of mind. Mental phenomena cannot be referred to bodily as effect to cause. Natural science presupposes a closed circle of movements governed by mechanics; motion can only derive from motion. Psychology must derive mental processes from other mental processes. Weber’s law was shown as a mathematical expression of the relativity of mental states; ideational connections were referable to association laws (likeness and contiguity); apperception laws and feelings were psychologically interpretable. Psychical can only be explained from psychical. Yet mental processes connect with definite physical processes, especially in the brain—a uniform co-ordination. This connexion is a parallelism of two causal series existing side by side without direct interference, termed psychophysical parallelism. Its validity cannot be doubted, but its extent requires consideration. From the physical side, vital phenomena form a narrow part of material processes; few have mental processes. The materialistic view that parallelism formulates causal dependence of mental on physical is inadmissible; mental existence did not suddenly appear but marks the limen of clearer conscious life. Primitive mentality was simple feeling and sensing, possibly accompanying every material movement-process. From the mental side, the older spiritualistic psychology restricted the connexion to sense-perceptions and voluntary actions, but recent tendencies extend it. Every conscious content with sensible attributes has a physical substrate. Memory images and sense-perceptions differ only in intensity of underlying excitation-processes. Intellectual processes cannot be excepted: every concept requires an idea with sensational content. Apperception and attention involve changes in sensational content, and volition implies alterations in ideational contents.
Old and New Phrenology
No mental process with sensational elements occurs without corresponding physical processes. But parallelism does not imply that the physical substrate is a localized organ in the brain in the manner of the old phrenology. The older view sought to assign each mental faculty to a distinct cerebral region, a doctrine that empirical evidence has discredited. The newer conception recognizes that while mental processes are uniformly co-ordinated with physical processes, the brain functions as a whole in its relation to consciousness. The parallelism holds between the totality of mental life and the totality of cerebral processes, not between individual mental elements and isolated brain centres. This holistic view avoids the errors of both materialism, which would reduce mind to brain activity, and spiritualism, which would deny any physical correlate to higher mental functions. The lectures thus conclude that the relation of mind and body is one of thoroughgoing correspondence without causal interference, leaving the ultimate nature of mind as a question that empirical psychology must acknowledge but cannot answer from its own resources.
