De Interpretatione or On Interpretation (Greek: Περὶ Ἑρμηνείας, Peri Hermeneias) is the second text from Aristotle's Organon and is among the earliest surviving philosophical works in the Western tradition to deal with the relationship between language and logic in a comprehensive, explicit, and formal way.
The work begins by analyzing simple categoric propositions, and draws a series of basic conclusions on the routine issues of classifying and defining basic linguistic forms, such as simple terms and propositions, nouns and verbs, negation, the quantity of simple propositions (primitive roots of the quantifiers in modern symbolic logic), investigations on the excluded middle (which to Aristotle is not applicable to future tense propositions—the problem of future contingents), and on modal propositions.
Chapters 6 and 7 deal with the relationship between affirmative, negative, universal and particular propositions.
The distinction between universal and particular propositions is the basis of modern quantification theory.
Aristotle defines words as symbols of 'affections of the soul' or mental experiences.
Spoken and written symbols differ between languages, but the mental experiences are the same for all (so that the English word 'cat' and the French word 'chat' are different symbols, but the mental experience they stand for—the concept of a cat—is the same for English speakers and French speakers).
A simple proposition indicates a single fact, and the conjunction of its parts gives a unity.
A universal term is capable of being asserted of several subjects (for example 'moon'—even though the Earth has one moon, it may have had more, and the noun 'moon' could have been said of them in exactly the same sense).
Aristotle enumerates the affirmations and denials that can be assigned when 'indefinite' terms such as 'unjust' are included.
In a single proposition, the nouns referring to the subjects combine to form a unity.
Thus, 'two-footed domesticated animal' applies to a 'man', and the three predicates combine to form a unity.
But in the term 'a white walking man' the three predicates do not combine to form a unity of this sort.
This chapter considers the mutual relation of modal propositions: affirmations and denials which assert or deny possibility or contingency, impossibility or necessity.
Robert Blanché published with Vrin his book Structures intellectuelles in 1966 and since then many scholars think that the logical square or square of opposition representing four values should be replaced by the logical hexagon which by representing six values is a more potent figure because it has the power to explain more things about logic and natural language.
Most important also is the immediately following Chapter 9 dealing with the problem of future contingents.
Aristotle's original Greek text, Περὶ Ἑρμηνείας (Peri Hermeneias) was translated into the Latin "De Interpretatione" by Marius Victorinus, at Rome, in the 4th century.