What Do a Greek and an English Sentence Share? Not the Words

The Stoics argued that any act of speech involves three things that must not be confused. There is the sound itself, which is a physical event in the air. There is the object referred to, which is a physical thing in the world. And there is what is conveyed, the content that a hearer who knows the language grasps and a hearer who does not fails to grasp, even though both hear exactly the same sound. That third item is the subject here. The argument for treating it as distinct is that a Greek speaker and a foreigner hearing the same words receive the same sound and the same object and differ only in the third.

The position created a serious problem inside Stoic philosophy itself:

• •The Stoics held that only bodies exist and only bodies can act
• •The content conveyed is plainly not a body
• •So it cannot be said to exist in their sense
• •They classified it instead as something that subsists
• •That put it in a small category with place, time and void
• •Critics attacked exactly that manoeuvre as an evasion

The distinction let the Stoics build a logic quite different from Aristotle's, and it was a substantial achievement. Because they identified the bearers of truth as complete contents rather than as sentences or as thoughts, they could treat whole statements as units and build arguments from relations between them, which is propositional logic. Their system handled conditionals, disjunctions and negations of whole statements, and the five basic argument forms they set out are recognisable as rules still taught. Aristotle's logic works with terms inside statements instead, which is a different and complementary approach, and the two were treated as rivals for centuries before both were absorbed into modern logic.

The Stoics divided the category in a way that maps onto modern grammatical analysis. An incomplete one is what a predicate on its own conveys, such as the content of the words is walking, which leaves the hearer waiting for something, and it is not the kind of thing that can be true or false. A complete one results when a subject is supplied, giving the content of a whole statement, and only those can bear truth. They further classified complete ones into statements, questions, commands, oaths and several other kinds, which is an early recognition that not every complete utterance is an assertion, a distinction that modern philosophy of language treats as basic.

The same three-way distinction was rediscovered and is now standard, which is why the ancient position is more than a curiosity. Gottlob Frege argued in 1892 that an expression has both a reference, meaning what it picks out, and a sense, meaning the way it presents that thing, using the example of two names for the planet Venus that refer to the same object while plainly differing in content. That distinction is the foundation of modern philosophy of language, and the parallel with the ancient position was noticed quickly. The question of what kind of thing a meaning is, given that it is neither a sound nor an object, remains open.

Separating the sound, the object and the content conveyed rests on the observation that a speaker and a foreigner hear the same sound and see the same object and differ only in the third item. Holding that only bodies exist forced the Stoics to classify that content awkwardly. The distinction let them treat whole statements as units and build propositional logic, and Frege reached a comparable position in 1892.