Esperanto vs Interlingua: Two Opposite Bets

Esperanto and Interlingua are the two serious survivors of the international auxiliary language project, and they are worth comparing precisely because they disagree about everything. Same problem, opposite bets. Esperanto bet on the learner. Interlingua bet on the reader. One of those bets built a community that is still holding congresses; the other built a beautiful proof of concept that almost nobody uses. We will make the case for which is which, but first the two designs deserve an honest hearing, because Interlingua is a far better piece of work than its obscurity suggests.

Where Interlingua came from

Interlingua was not one person's project. The International Auxiliary Language Association (IALA) was founded in New York in 1924, bankrolled largely by the heiress Alice Vanderbilt Morris, with a mandate to settle the auxiliary language question scientifically. It spent over two decades on research, with serious linguists (André Martinet among them) passing through its research directorship, before Alexander Gode led the final phase and published the result in 1951: the Interlingua-English Dictionary and its accompanying grammar.

The method is the interesting part. IALA did not invent words; it extracted them. Take a set of control languages: English, French, Italian, and Spanish/Portuguese counted as one unit (with German and Russian consulted as backups). A word qualifies for Interlingua if variants of it appear in enough of the control languages, and it enters the dictionary in its prototype form, the shape closest to the common ancestor of its living variants. The vocabulary of Interlingua is, in effect, the international scientific and Romance word stock of Europe, systematically harvested and standardised. The grammar keeps only features shared across the control languages, so noun gender, case endings and person conjugation are gone.

The result reads like this: Interlingua es un lingua auxiliar international basate super le vocabulario commun del linguas europee. If you can read that without ever having seen Interlingua before, you have understood the whole design philosophy, because that is the point: at-sight intelligibility. An educated speaker of Spanish, Italian, French or Portuguese, and to a large degree English, can read Interlingua with no study whatsoever. It genuinely works. In the 1950s and 60s, scientific and medical publications carried Interlingua abstracts on exactly this logic: print the summary once, in a language every European researcher can read unstudied.

The paragraph Latino sine flexione earned

Interlingua's core idea had a proof of concept half a century earlier. In 1903 the great Italian mathematician Giuseppe Peano, of the axioms, proposed Latino sine flexione: keep Latin's vocabulary, which Europe's educated classes already shared, and simply delete the inflections, the case tables and conjugations that make Latin expensive. Peano's academy adopted the name Interlingua for it, decades before IALA borrowed the word. Latino sine flexione was used in mathematical papers, mostly Peano's own circle, and faded after his death in 1932. It matters here as the thesis statement IALA later engineered properly: it demonstrated that a language assembled from already-international material can be read without being learned. IALA's contribution was to replace Peano's classical Latin base with the living, statistically extracted word stock of modern Europe.

Esperanto's opposite bet

Esperanto, thirty-seven years older than IALA, is built on the reverse philosophy: schematic design. Zamenhof took European roots but reshaped everything to fit an invented, exceptionless system. Sixteen rules. No irregular verbs at all. One article. Phonetic spelling. And the crown jewel, a fully productive affix system: learn bona (good) and the affixes hand you malbona (bad), boneco (goodness) and plibonigi (to improve) without opening a dictionary.

The cost is that Esperanto is nobody's freebie. Malsanulejo (hospital: un-health-person-place) is transparent to an Esperantist and opaque to everyone else, where Interlingua's hospital is free to half of Europe. Esperanto asks everyone, Romance speaker or not, to pay the same entry fee.

The payoff is what the fee buys. Because the system is exceptionless, the fee is small: 150 to 200 hours to comfortable conversation, against roughly 600 to 750 for Spanish or French. And it buys production, not just recognition. The affix system means a modest root vocabulary multiplies into a large expressive one; the regular grammar means you can build sentences confidently from day one rather than pattern-matching against half-remembered Romance.

The honest scorecard

• Reading, unstudied: Interlingua, by a mile. This is its designed superpower and it delivers.
• Speaking and writing: Esperanto. Interlingua's naturalism means its derivation is irregular in exactly the way natural languages are; you memorise word families rather than generating them. Esperanto's learner reaches active use faster and with more confidence.
• Fairness: Esperanto, with a caveat. Interlingua is nearly free for a Milanese doctor and full price for a Japanese one. Esperanto's vocabulary is also thoroughly European, so its neutrality is relative, but at least its machinery favours nobody.
• Community: Esperanto, overwhelmingly, and this is the decisive column. Speaker estimates for Esperanto run from tens of thousands of fluent speakers to a couple of million with some competence, with a world congress running since 1905, original literature, music, a hospitality network and native speakers. Interlingua's community, organised around the Union Mundial pro Interlingua, is measured in the hundreds. It has enthusiasts; it does not have a world.

Notice what happened: Interlingua wins the category it was designed to win, and Esperanto wins the categories that make something a language rather than a notation. A language you can read but will never speak to anyone is a cipher for text you could mostly have guessed anyway. The whole point of a shared second language is the sharing.

Which to learn

If you are a linguist, read about both; Interlingua's extraction method is one of the most elegant things the field produced and an afternoon with it costs you nothing, which is rather the point of it. But if you are choosing a constructed language to actually learn, the comparison is not close. Esperanto is the one with people in it, and that is the reason worth learning any auxiliary language.

Our Esperanto course is built frequency-first: the 1,000 most useful words taught in order of how often you will meet them, audio in two accents on every word, a dedicated affix track that turns each root into a family, graded stories at strict vocabulary ceilings, and a complete grammar section. It is the schematic bet, taken seriously. Interlingua proved Europe could read a common language without learning it. Esperanto proved people would learn one, and that is the better half of the miracle.

Cross-references

• Esperanto vs Ido - the 1907 schism, and why reforming Esperanto failed.
• Toki Pona vs Esperanto - minimalism vs a working language.
• Why learn Esperanto? - the honest case, both ways.
• Is Esperanto easy to learn? - what the sixteen rules actually buy.
• How long does it take to learn Esperanto? - the hour arithmetic.
• How many people speak Esperanto? - the community numbers, honestly handled.
• The Esperanto course - where the actual learning happens.