XXXVIII. On the subject of logical speculation, there appears to be a great unanimity among the greater part of the Stoics, in beginning with the topic of the voice. Now voice is a percussion of the air; or, as Diogenes, the Babylonian, defines it, in his essay on the Voice, a sensation peculiar to the hearing. The voice of a beast is a mere percussion of the air by some impetus: but the voice of a man is articulate, and is emitted by intellect, as Diogenes lays it down, and is not brought to perfection in a shorter period than fourteen years. And the voice is a body according to the Stoics; for so it is laid down by Archedemus, in his book on the Voice, and by Diogenes, and Antipater, and also by Chrysippus, in the second volume of his Physics. For everything which makes anything, is a body; and the voice makes something when it proceeds to those who hear from those who speak. A word (λέξις), again, is, according to Diogenes, a voice consisting of letters, as “Day.” A sentence (λόγος) is a significant voice, sent out by the intellect, as for instance, “It is day;” but dialect is a peculiar style imprinted on the utterance of nations, according to their race; and causes varieties in the Greek language, being a sort of local habit, as for instance, the Attics say θάλαττα, and the Ionians say ἡμέρη. The elements of words are the twenty-four letters; and the word letter is used in a triple division of sense, meaning the element itself, the graphical sign of the element, and the name, as Alpha. There are seven vowels, α, ε, η, ι, ο, υ, ω; six mutes, β, γ, δ, κ, π, τ. But voice is different from a word, because voice is a sound; but a word is an articulate sound. And a word differs from a sentence, because a sentence is always significative of something, but a word by itself has no signification, as for instance, βλίτρι. But this is not the case with a sentence. Again, there is a difference between speaking and pronouncing; the sounds are pronounced, but what are spoken are things which are capable of being spoken of.