Galen was no sceptic. On several occasions he refers derisively to ‘boorish Pyrrhonists’, suggesting that scepticism, at least in its more extreme forms, is a matter of a lack of culture, an intellectual infantile disorder. Time and again, he stresses that, if only the inquirer is blessed with diligence, honesty and intelligence, and armed with the proper logical tools of rational discourse, he can aspire to a genuine understanding of the way in which the physical (or more particularly the physiological) world works. In Elements According to Hippocrates (Hipp.Elem.), he argues that the successful medical practitioner needs to know the fundamental elements that make up physical objects, and how they interrelate to one another (although as we shall see, there are some qualifications to this necessity); he affirms that it is demonstrable that monism is false; and even more strikingly affirms that Hippocrates himself (in Nature of Man) demonstrated its falsity (Hipp.Elem. I.415–16; cf. 416–42). In a similar vein, On Mixtures (Temp.) talks of the importance of understanding the real states of affairs in regard to the internal mixtures of the body and its various properties, phenomenal and causal, and of properly assessing the varying degrees of heat, cold, dryness and moisture of the various parts. Another ‘physical’ treatise, On the Natural Faculties (Nat.Fac.), argues for the reality of certain fundamental natural capacities (attraction, retention, alteration and expulsion) possessed by distinct parts of animals' bodies in virtue of which they can perform their functions, and against what he stigmatises as the excessively crude materialism of the atomists and their various anti-teleological acolytes.