CHAPTER THREE
CHRYSIPPUS AND SCIENCE
The physician Praxagoras of Cos (later 4th c. BCE) has been plaus ibly identified as one of the main influences on Stoic physical psychology.1 In PHP I Galen takes issue with Praxagoras' view of the arteries, primarily, he says, because Chrysippus referred to it (PHP I 7.1 = SVF II 897, fourth text). According to Praxagoras, the arteries end in what he called vEupa.2 There is an ambiguity involved here, because Praxagoras, like Aristotle, had not yet arrived at a distinct concept of nerves; for him, the concept of VEupa also covered sinews and ligaments.3 Galen draws a distinction between the structures concerned in his discussion of Aristotle's observation of vEupa on the heart (I 9): what Aristotle saw were not nerves but what Herophilus had called 'nerve-like strands' (I 10.1- 5). 4 In connection with Praxagoras' position, however, Galen is silent about the difference from later usage, presumably because he has no polemical interest in pointing it out here. On the other hand, he is generous in supplying information on the anatomy of the arteries according to Praxagoras. From this it is clear that they functioned as the means of communication through which volun tary movement is imparted to the body from the heart.5 In Chrysippus' lifetime, Praxagoras' doctrine may already have represented a traditional and fairly authoritative paradigm of human physiology, with many centuries of influence still ahead, but also under pressure from the more recent discoveries made in Alexandria. There is an interesting passage from the On the Passions (PHP IV 6.5-6 = SVF III 473) where Chrysippus remarks that the terms 'tovo~ ('tension'), a'tovo~ ('with weak tension') and
I See supra, pp. 83 ff. 2 Cf. Foet. Form. IV p. 674 K. (SVF II 761): Ti no1' ol)v i::oo~e Xpucrinmp ... U7tO 6 On the metaphorical use of -r6vo~ and veupov see also Vegetti ( 1990), who however does not take account of Praxagoras' influence on Stoic conceptions; cf. Mansfeld ( 1992a). 7 Note esp. ( 1) the idea of -r6vo~ involved here; (2) Chrysippus' reference to av9e~et ('holding fast'), which recalls Praxagoras' emphasis on the evidence of the hands, cf. fr.l1 St. Yet the fact that this conception was similar to those of other authorities should warn us not to be too quick to speak here in terms of specifically Praxagorean influence on Chrysippus; cf. e.g. Aristotle's view. 8 See supra, pp. 148, 155; cf. 144.