Aristotle’s (384–322 BC) De Interpretatione (Περὶ ἑρμηνείας, “On Interpretation”) is a small work at the foundation of logic. It is Book II of the Organon, the group of logical works, placed just after the Categories. Fourteen short chapters, each with clause piled on clause. The subject: how words come to mean anything, and where truth and falsity arise.
His teacher Plato left “is a name natural or conventional?” open in the Cratylus (article 041). Aristotle answers it in a single line.
1. The chain of meaning — things, mind, sound, writing
Ἔστι μὲν οὖν τὰ ἐν τῇ φωνῇ τῶν ἐν τῇ ψυχῇ παθημάτων σύμβολα, καὶ τὰ γραφόμενα τῶν ἐν τῇ φωνῇ.
Spoken sounds are symbols of the affections in the soul, and written marks are symbols of spoken sounds. (ch. 1, 16a; Greek quotations throughout, Japanese and English are L/LAB working translations.)
Sounds and letters differ from one people to the next. But what they primarily point to — “the affection in the soul” — is the same for all, and so is the “thing” that the affection copies. So Aristotle lays it out.
2. “By convention” — the answer to Cratylus
The definition of the noun (ὄνομα) turns on one phrase: “by convention” (κατὰ συνθήκην).
Τὸ δὲ κατὰ συνθήκην, ὅτι φύσει τῶν ὀνομάτων οὐδέν ἐστιν, ἀλλ᾿ ὅταν γένηται σύμβολον.
“By convention” — because no name exists by nature, but only when it becomes a symbol. (ch. 2, 16a)
The cries of animals (ἀγράμματοι ψόφοι) also express something. But they are not names. A name is what “becomes a symbol” by the convention of a community. To the pair of options Plato held open, Aristotle rules for nomos (article 043). That ruling stays the Western mainstream until Saussure rebuilds it as a first principle, 2,000 years later.
3. Truth lives only in the sentence
“Human” alone, “white” alone, assert nothing yet. Truth and falsity arise when they are combined (σύνθεσις) or separated (διαίρεσις) — “a human is white,” “a human is not white.” And not every sentence (λόγος) has a truth-value. “A prayer is a sentence, but neither true nor false” — prayers, commands and questions belong to rhetoric and poetics; what logic handles is only the assertion (λόγος ἀποφαντικός) (article 045).
4. Will there be a sea battle tomorrow?
Chapter 9 poses the most famous problem in the history of logic. Is the sentence “there will be a sea battle tomorrow” already true or false, now? If every sentence is already settled as true or false, then everything about tomorrow happens of necessity, and deliberation and action are pointless. Aristotle’s answer (its reading is disputed): the whole “there will be a sea battle tomorrow or there will not” is necessary, but neither disjunct is now true (article 047).
In sum
| Question | The answer in De Interpretatione |
|---|---|
| How do words mean? | Sound is a sign of the soul’s affection, writing a sign of sound. By convention |
| Natural or conventional? | Convention. “No name exists by nature” |
| Noun vs. verb | The verb co-signifies time (προσσημαίνει χρόνον) |
| Where does truth live? | Not in words but in the assertion that combines or separates them |
| Prayers and commands | Sentences, but with no truth-value. To rhetoric and poetics |
| Is a future sentence already true? | The disjunction is necessary; each disjunct is undetermined (the sea-battle problem) |
Why it is still read
- The starting point of logic — the framework of affirmation, negation, contradiction, universal and particular runs, by way of the medieval “square of opposition,” straight into the elements of modern logic.
- The unit called “the proposition” — the cut that says truth is borne by the sentence, not the word, runs in one line to Wittgenstein’s Tractatus and “the proposition is a picture of reality.”
- The arbitrary sign — “by convention” stayed the ground of how language was seen until Saussure rebuilt it as a first principle.
- The future and determinism — the sea-battle chapter keeps generating debate: the Stoics, medieval scholasticism, and Łukasiewicz’s three-valued logic (true, false, undetermined) in the twentieth century.
