Giuseppe Peano’s Interlingua is a short, combative treatise from the Academia pro Interlingua in Cavoretto–Torino, written by the Turin mathematician and professor himself. It sets out a complete design for an international auxiliary language: an international vocabulary, Latin orthography, and no grammar at all. Peano writes the argument in his own “latino sine flexione,” so the book demonstrates its thesis on every page even as it defends it.
The Case Against Babel
Peano opens with history. Latin served as the common language of learning from the Roman empire through the Middle Ages and into the science of the last century; Leibniz, Newton, Euler, and Gauss wrote almost entirely in it. Today, by contrast, authors publish in a scatter of national tongues—Neo-Latin, Germanic, Slavic, even Japanese—and this multitude of languages in work of common human interest is, he says, a great obstacle to progress.
He then sorts through the standard proposals and finds each wanting. A return to scholastic Latin fails because its advocates do not follow their own advice: eight years of school Latin does not suffice to possess the language. Adopting one national language fails too—one can learn to read a foreign language fairly quickly, but writing it correctly under its grammar rules takes many years. That leaves artificial languages, and here Peano turns to precedent. Descartes in 1629 imagined a language the public could read and write after six hours of study with only a vocabulary, one in which “a rustic man can judge of truth better than the philosophers of today.” Leibniz set out profound ideas on the question and, in manuscripts published only in 1903, proposed a rational grammar with a Latin vocabulary—no declension, no plural, no abstract forms. But the rational language stayed in the minds of philosophers.
Volapük’s Rise and Fall
The first artificial language to reach the public was Volapük. Schleyer, a parish priest at Konstanz, published its first book in 1879, drawing words from natural languages—Latin, English, Italian, German, Russian—with a phonetic orthography and a machinery of case vowels, a plural in -s, tense prefixes, and a system of prefixes and suffixes for mood and derivation. Peano gives the Lord’s Prayer in Volapük to show both its reach and its opacity: one who does not know the key understands nothing.
The movement’s growth was remarkable. Kerkhoffs, a Paris professor of languages, published a manual, a vocabulary, and a periodical in 1886; by 1889 there were 283 Volapük societies across five continents, over 1,600 certified professors, 316 manuals (182 of them in 1888 alone), and 25 periodicals, four in Italy. Then came the unraveling. Kerkhoffs proposed simplifying the grammar, others proposed graver changes, and a multitude of rival languages sprang up—Esperanto among them, in 1887. Delegates at the second congress in Munich, in August 1887, founded the Academia pro Interlingua, with Schleyer as president and Kerkhoffs as director; the third congress in Paris, 1889, approved its statute.
The International Vocabulary
The heart of Peano’s program is the vocabulary. He praises Canesi’s 1921 Torino dictionary—10,000 Anglo-Latin words in triple Latin-Italian-English orthography—as convenient and sufficient for all use, and argues that a writer may simply adopt Latin words as they appear in his own language’s etymological vocabulary. Studying Interlingua thus means studying the etymology and exact value of words in one’s own tongue. Chemistry’s symbols are already universal (Au for gold), as are botanical and zoological names (canis, vulpes; cofea, thea).
Volapük, by contrast, is criticized for its 1,400 radicals drawn from Latin, English, and others with no visible rule—naming the sun by a Latin word and the moon by an English one—which provoked a “babel of artificial languages” when later designers reversed the choice. In 1889 J. Lott, a railway constructor in Vienna, demonstrated an international vocabulary intelligible to every cultured person without study; Liptay, a physician in Chile, and others reached the same result. Between 1893 and 1898 the Academia collected 4,500 international words in its circulars, and its 1895 example, rendered in Latin-derived form, shows the words are equally Italian, French, English—the international vocabulary is evidently Latin, and a document for the history of European civilization.
Orthography and the Latin Theme
On spelling, Peano’s reasoning is etymological: anyone who knows a European language knows that rosa, rose, and their kin derive from Latin rosa, and Latin orthography yields the modern orthographies, so the Academia recommends Latin spelling. Where a word has a single Latin form, it is listed as is (ad, in, ei, non, semper, fieri, decem). Where forms multiply, the theme—the ablative—is adopted (rosa, anno, dente, sensu, die, novo, me, te, se, illo, uno), or the nominative when the word has no suffix (prisma, nos, vos, duo, qui, breve), or the imperative (ama, habe, scribe, audi, es, fi), with irregulars like imita, vol, pote, que from quem. Themes are derived by stripping -m, -s, -re, -t. The Latin theme, not the nominative, lives on in modern languages; Peano quotes Skeat’s 1888 dictionary calling the practice of citing the Latin nominative “a mere absurdity.”
Practical aids follow. Peano himself (1909, 1915), Pinth, Basso, and Canesi published international words as Latin themes in alphabetical order, so that one such vocabulary suffices to read and write Interlingua. For those with only a school Latin dictionary, he gives rules: genitive endings -ae, -i, -is, -us, -ei yield themes in -a, -o, -e, -u, -e, with adjectives, pronouns, and verbs (infinitive minus -re) treated the same way, irregulars included. Words absent from Latin dictionaries—logarithmo, oxygenio, telegrapho, radiophonia, aeroplano, interlingua; algebra, cifra, cofea, thea; club, buffet, albino, allegro—are known without consultation. A writer may adopt any word he prefers, provided he explains it where the reader might not understand.
The Academy’s own record here is a cautionary tale: Volapük had no orthography rules, and the Academia’s successive reforms of 1895 and 1902—changing ae/oe to e, ph to f, c to k or s, suppressing final vowels, simplifying double consonants, then changing the rules again—rendered previous publications commercially worthless. Only in 1909–1912, after long discussion, did it approve the Latin theme.
The Language Without Grammar
Grammar, Peano argues, is a torment of childhood and nearly always useless. Strip Italian to its dictionary forms and you get something serviceable; do the same to French and you get “petit nègre,” convenient for anyone who cannot spend years mastering 2,265 verb forms. English without grammar is nearly true English. Chinese has no grammar; mathematical formulas are grammarless propositions; a traveler with a hundred words can speak and be understood. Publishing a book in a national language without grammar would be indecent, like walking publicly against custom—but undeterred by Cicero and Horace, Peano reduces all words to themes and produces “latino sine flexione”: Me scribe, Te lege, Nos habe uno lingua et duo aure. Grammar is not always dispensable: where suppression confuses singular and plural, past and future, active and passive, the sentence is recast. He quotes Bertrand Russell’s Principles of Mathematics (1903) on grammar being excellent in proportion to the paucity of its inflexions, and insists that the distinctions among parts of speech are relative to inflected languages and have no logical value—a point, he says, well known to linguists, rendering the whole grammatical nomenclature valueless.
Participles, the Passive, and Quem
The closing stretch works through the constructions that a grammarless Latin most strains to express. Laborare est orare equals qui labora ora. The Latin participle in -nte survives internationally (adjutante, agente, assistente) and can be rendered by que, qui, quod: vacante = que vaca, studente = qui stude. Seneca’s Ducunt volentem fata, nolentem trahunt becomes Fato duce qui vol, trahe qui ne vol.
The Latin passive—amor amaris amatur—is dead, Peano declares. Modern languages mark the passive with the participle, which in Latin carries the suffix -to; adding -to to the verb theme satisfies the complicated rules (scribe scripto, rumpe rupto, fer lato), but the Academy’s 1890 attempt to regularize the passive participle produced artificial words. The natural solution is to adopt the Latin participle unmodified, since it is almost always already international (allude/allusion, describe/description, frangible/fracture); about a hundred Latin verbs have double international forms from present and supine.
Better still, convert the passive away. Filio es amato ab matre becomes Matre ama filio; Fortes fortibus creantur becomes Homine forte crea forte; Seneca’s Avarus nullo satiatur lucro becomes Nullo lucro satia avaro. Where no subject exists, write nos, homo, or se—and Peano carefully distinguishes homo (French on, English man) from homine (French homine, German Mann). Cicero, the Vulgate, and the proverb Similia similibus curantur are all recast in turn: Nos cura simile per simile.
Finally, quem, the accusative of que, can itself mark the passive participle: quem ama = amato, quem rumpe = rupto. It survives in Spanish quien, Portuguese quem, French que, and shares its origin with English whom. Plautus’ Quem Di diligunt, adolescens moritur becomes Quem deos ama, mori juvene; Laberius’ warning about the man many fear becomes Quem multos time, debe time multos; Matthew VII.1 becomes Qui judica fi quem judica. Where quem would be ambiguous, one may write que in the pattern “que-subject-verb”: Petro, que Paulo ama means Paul loves Peter, while Petro, que ama Paulo means Peter loves Paul. The gerund yields to the same treatment—Docendo discitur becomes Qui doce, disce; Fama crescit eundo becomes Fama cresce dum i; De gustibus non est disputandum becomes Nos ne debe disputa de gustu—and the notes break off mid-quotation of Virgil, at the very end of the book.
A Manifesto With a Working Demonstration
Interlingua is less a textbook than a manifesto with a working demonstration attached. Its central claim is that an international language need not be invented at all: it already exists, buried in the Latin-derived vocabulary that every European language carries, and the designer’s only task is to strip away inflection and let the themes stand bare. Peano’s mathematical instincts show everywhere—in the drive to eliminate redundancy, in the appeal to Russell, in the treatment of grammar as a needless complication to be converted away rather than learned. The book also carries a polemical edge: the history of Volapük serves as an object lesson in what happens when a language movement multiplies reforms faster than it can hold adherents, and the Academia’s own repeated reversals on orthography are admitted with disarming candor.
Peano Among the World-Language Schemes
The book belongs to the crowded decades around 1900 when Volapük, Esperanto, and a swarm of rivals competed for the title of world language, and it records that moment from the inside—congresses, circulars, vocabularies, and all. Peano’s “latino sine flexione,” later known as Interlingua, never displaced Esperanto, but its underlying insight, that the international scientific vocabulary is already Latin and needs only minimal grammar to function, influenced later naturalistic projects. For readers today the book is a curious hybrid: a mathematician’s proof, a reformer’s pamphlet, and a Latin exercise book, all written in the very language it proposes.
