on the subject of phantasia, and sensation, and thought.
XXXVII. They say that the proper criterion of truth is the comprehension, φαντασία; that is to say, one which is derived from a real object, as Chrysippus asserts in the twelfth book of his Physics; and he is followed by Antipater and Apollodorus. For Boethus leaves a great many criteria, such as intellect, sensation, appetite, and knowledge; but Chrysippus dissents from his view, and in the first book of his treatise on Reason, says, that sensation and preconception are the only criteria. And preconception is, according to him, a comprehensive physical notion of general principles. But others of the earlier Stoics admit right reason as one criterion of the truth; for instance, this is the opinion of Posidonius, and is advanced by him in his essay on Criteria.
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