De Interpretatione Ch. 1 - "Introducing the Proposition" - Aristotle

Chapter 1 - An Introduction to Making a Sentence

Aristotle is clearly transitioning here from defining individual words to building a sentence, hence we need to understand the fundamental components of a sentence. These are nouns and verbs (which include affirming or negating). The written word is a symbol of the spoken sound, which is a symbol of the idea, which is the representation of the actual thing. These words, by themselves, do not have truth or falsehood implied in them, but when "composition" or "division" take place, then truth or falsity comes along. In other words, when we form a proposition, we are now making a truth claim with it about reality. 

The Text

"Let us, first of all, define noun and verb, then explain what is meant by denial, affirmation, proposition and sentence. Words spoken are symbols or signs of affections or impressions of the soul ; written words are the signs of words spoken. As writing, so also is speech not the same for all races of men. But the mental affections themselves, of which these words are primarily signs, are the same for the whole of man-kind, as are also the objects of which those affections are representations or likenesses, images, copies.

With these points, however, I dealt in my treatise concerning the soul; they belong to a different inquiry from that which we now have in hand. As at times there are thoughts in our minds un- accompanied by truth or by falsity, while there are others at times that have necessarily one or the other, so also it is in our speech, for combination and division are essential before you can have truth and falsity. A noun or a verb by itself much resembles a concept or thought which is neither combined nor disjoined. Such is ' man,' for example, or ' white/ if pronounced without any addition. As yet it is not true nor false. And a proof of this is in the fact that "tragelaphos," while it means something, has no truth nor falsity in it, unless in addition you predicate being or not-being of it, whether generally (that is to say, without definite time-connotation) or in a particular tense."