[125] Further particulars may be obtained in Schmidt’s Stoicorum Grammatica (Halle, 1839); Lersch, Sprachphilosophie der Alten; Steinthal, Gesch. der Sprachwissenschaft, i. 265–363; Nicolai, De Log. Chrys. Lib. 31. This part of dialectic began with enquiries into the voice and speech. Voice is defined to be sound and speech, to be air in motion, or something hearable—ἀὴρ πεπληγμένος ἢ τὸ ἴδιον αἰσθητὸν ἀκοῆς; the human voice as ἔναρθρος καὶ ἀπὸ διάνοιας ἐκπεμπομένη, is distinguished from the sounds of other animals, which are ἀὴρ ὑπὸ ὁρμῆς πεπληγμένος (Diog. 55; Simpl. Phys. 97; Sext. Math. vi. 39; Gell. N. A. vi. 15, 6). That the voice is something material is proved in various ways (Diog. 55; Plut. Plac. iv. 20, 2; Galen, Hist. Phil. 27). The voice, in as far as it is ἔναρθρος, or composed of letters, is called λέξις; in as far as it expresses certain notions, it is λόγος (Diog. 56; Sext. Math. i. 155). A peculiar national mode of expression (λέξις κεχαραγμένη ἐθνικῶς τε καὶ Ἑλληνικῶς ἢ λέξις ποταπὴ) was called διάλεκτος (Diog. 56). The elements of λέξις are the 24 letters, divided into 7 φωνήεντα, 6 ἄφωνα, and 11 semivowels (Diog. 57); the λόγος has 5 parts, called στοιχεῖα by Chrysippus—ὄνομα, προσηγορία, ῥῆμα, σύνδεσμος, ἄρθρον—to which Antipater added the μεσότης, or adverb (Diog. 57; Galen, De Hippocrat. et Plat. viii. 3; Lersch, ii. 28; Steinthal, 291). Words were not formed by caprice, but certain peculiarities of things have been imitated in the chief sounds of which they are composed. These peculiarities can therefore be discovered by etymological analysis (Orig. c. Cels. i. 24; Augustin. Dialect. c. 6; Opp. T. I. Ap. 17, c.). (Chrysippus, however, observes (in Varro, L. Lat. ix. 1) that the same things bear different names, and vice versâ, and (in Gell. N. A. xi. 12, 1) that every word has several meanings.) See Simpl. Cat. 8, ζ. Five advantages and two disadvantages of speech are enumerated Diog. 59; Sext. Math. i. 210; and poetry (Diog. 60), various kinds of amphibolia (Diog. 62; Galen, De Soph. P. Dict. c. 4), the formation of conceptions, and division, are treated of. [126] Diog. vii. 54. [127] The statements of Zeno and Cleanthes, for instance, in reference to φαντασία, prove that these Stoics deduced their theory of knowledge from general principles respecting notions. They therefore started from the data supplied by the senses. A passage in Zeno, explaining the relations of various forms of knowledge, shows that even Zeno required progress to be from perception to conception and knowledge, and that he distinguished these states only by the varying strength of conviction which they produced.