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Oxf Stud Anc Philos. Author manuscript; available in PMC 2010 November 10.
Published in final edited form as:
Oxf Stud Anc Philos. 2009 July 1; 36: 283–320.
PMCID: PMC2977080
EMSID: UKMS28665

THE QUALITATIVE STATUS OF THE ONKOI IN ASCLEPIADES' THEORY OF MATTER

Abstract

The medical and philosophical system of Asclepiades of Bithynia (fl. later second century BC)1 has been the subject of considerable controversy.2 His physical theory of anarmoi onkoi in particular has seen intense debate, and although many of its broader features appear to be fairly well established, many of its most fundamental details remain obscure. Perhaps somewhat paradoxically, some of the most important work carried out on Asclepiades has been explicitly focused instead on Heraclides of Pontus,3 the reconstruction of whose physical theory has often proceeded on the assumption that this was largely replicated by Asclepiades some two centuries later. But to a great extent the Asclepiadean debate has been framed in terms of the question of his intellectual debts to ancient atomism, and Epicureanism in particular, and in this respect the present study will be no different.4 The most recent scholarship has been sharply divided over this question. Vallance has emphasized the principally medical context of Asclepiades' system, and made the case that the frangibility of the onkoi marks such a fundamental divergence from Epicurus' atomism that any influence from Epicurean physics should be rejected, and that we should look instead especially to Erasistratus.5 Casadei, however, following on to a certain extent from the work of Pigeaud, has rightly drawn attention to the tendency in Vallance's exposition to suppress a number of fundamental elements of Asclepiades' doctrine which are undeniably also distinguishing features of Epicurean philosophy.6 The most significant of these include his particulate theory of matter, his antiteleological conception of nature, and his rejection of any theory of qualitative change. But these correspondences would certainly not be sufficient to qualify Asclepiades' system simply as a reproduction of Epicureanism, and there is clear evidence that Asclepiades stood in opposition to Epicurus in certain fundamental respects. In a recent study which has done much to establish Asclepiades' credentials as a philosopher, focusing especially on his philosophy of mind, Polito has underlined certain distinctly non-Epicurean elements in his system, such as his radical determinism and his denial of a localized ruling-part-of-the-soul.7 It thus seems clear that, despite some important parallels between their systems, Asclepiades cannot be regarded as an Epicurean physician. The evidence we have for his doctrine, and the authority which was accorded him by later writers, clearly attests to his status as an independent and innovative thinker in his own right. While Asclepiades' theory must, in my view, be analysed within the context of the Epicurean atomistic tradition, it must equally be acknowledged that any identifiable relationship between Epicurus and Asclepiades is likely to be one of considerable complexity.

In this paper I shall attempt to explore further the nature of the relationship between Epicurus and Asclepiades by examining some aspects of the latter's theory of matter. Given the widespread disagreement about his theory in general, I propose to focus on a fundamental question which I believe the extant evidence allows us to answer with a satisfactory degree of certainty, namely what Asclepiades' position was on the qualitative status of his onkoi. In Section I I shall analyse four passages which have a direct bearing on this question, from Caelius Aurelianus, Galen, Sextus Empiricus, and Calcidius respectively. I shall argue here that this position was in its details substantially the same as Epicurus' with regard to his atoms. It must be stressed that it is only in details that we can make such comparisons, since we have no surviving testimony which recounts Asclepiades' arguments or broader reasons for holding such a position. Nevertheless, in Section II I shall argue that these identifiable similarities in their respective doctrines on the qualities of their elements were more than superficial or incidental, and strongly suggest that Asclepiades and Epicurus shared certain premisses which were fundamental to their physics, which might then be used to contextualize and elucidate some of the more idiosyncratic and apparently unique parts of Asclepiades' system. This will lead me to suggest an interpretation of an important piece of evidence which may confirm that Asclepiades was reacting in a direct and critical way to certain aspects of Epicurus' physical doctrine.