Diogenes of Apollonia (5th century bc)
Diogenes was the last of the early Greek physicists. He claimed that interactions between things would be impossible unless all were forms of one basic substance. Adapting ideas of Anaximenes and Anaxagoras, he identified the basic substance as air, which in its optimal form possesses intelligence and thereby controls the universe at large and animal life in particular. Diogenes worked out a detailed psychology and physiology, explaining sense perception as an exercise of intelligence due to interaction between air in the region of the brain and atmospheric air. This theory was mocked by Aristophanes, but influenced various Hippocratic writings.
1 Life and work
Almost nothing is known of Diogenes’ life. His birthplace Apollonia was probably the Milesian colony of that name on the Black Sea. Diogenes Laertius (IX 57) dates him to the same period as Anaxagoras (500–428 bc). Aristophanes’ allusion to his ideas ( Clouds 227–33) and Theophrastus’ statement that he was pretty much the last of the Presocratics (A5 ) suggest someone younger. Simplicius attributes the surviving fragments to a general work on nature (A4), but the sequence of topics would seem to point to another of the treatises by Diogenes – On the Nature of Man – as their probable source.
Diogenes is elsewhere credited like the atomists with belief in an infinite number of worlds, and with a cosmogony and account of the earth and the heavenly bodies which largely recapitulate Anaxagoras’ theories ( A1, A6, A12) (see Anaxagoras §4). Indeed, Theophrastus explicitly represented him as drawing eclectically from these two major fifth-century systems (A5). But the work from which Simplicius quotes evidently had a quite different theme. It began with metaphysical argument for the fundamental identity of all physical things (fr. 2). Then, consequent upon proofs that the universe is permeated with intelligence (frs 3 and 4), it contended that the seat of intelligence is air, which is a single substance, despite variations in temperature, moisture and mobility etc. (fr. 5). Simplicius assures us that this substance is the eternal imperishable body whose existence was derived a priori in the opening argument (frs 7 and 8 ).
There followed a sequence of proofs designed to substantiate the dependence of animal life and intelligence upon air. Simplicius mentions demonstrations that sperm is aerated and that acts of intelligence occur when air via blood takes possession of the whole body. He refers to an anatomy of the human veins, which is preserved more or less verbatim by Aristotle (History of Animals III 2, see Diogenes fr. 6). Diogenes probably gave his account of sense perception, extensively reported by Theophrastus (A19 ), at this point in the book, along with discussions of physiological phenomena like sleep and digestion.
These detailed explanations appear to have constituted the real focus of the work. Its structure is just what one might expect of a fifth-century book ’on the nature of man’: Polybus, author of the Hippocratic treatise bearing this title, complains of the way some writers on human physiology preface their accounts with grandiose claims, supported by meaningless proofs, about a single basic substance.
2 Monism
Ancient and modern historians of philosophy alike see Diogenes’ theory as reviving the system of Anaximenes a century earlier (see Anaximenes §1). But it is a revival informed by reflection on more recent philosophy. Thus the argument for Monism found in fragment 2 has clear affinities with theses of Anaxagoras and Democritus, although Democritus may depend on Diogenes; there are also verbal echoes of Melissus and Empedocles. Diogenes proposes that two objects cannot mix with or benefit or harm each other, nor can one grow or be born from another, unless they are really – ’in their nature’ – the same. Since he assumes that the four elements all do interact with one another, he concludes that all of them, and therefore all things whatsoever, are forms of the same basic substance. Diogenes’ monism therefore allows for a world of variety and change. Nor does he acknowledge any need to rebut Melissus’ proofs of the logical impossibility of alteration, even if the wording of fragment 2 betrays his familiarity with them.
Diogenes’ arguments that there is ’much intelligence’ in the basic substance recall Heraclitus as well as Anaxagoras. He appeals principally to the optimal disposition of day and night and the seasons, but also to the role of soul and intelligence in sustaining animal life ( frs 3 and 4 ). Yet this is only preparatory to enunciation of his main thesis: the identification of air as what possesses intelligence. Once again Diogenes echoes Anaxagoras ( fr. 12: see Anaxagoras §4), but this time to subvert his insistence that mind (nous) is something pure from admixture with any other kind of substance. For Diogenes it is not mind, but the air that is its physical seat which permeates all things and thereby organizes and controls them. It is accordingly air that is to be regarded as what is strong and eternal and ’knowing many things’ (fr. 8 ), and as thereby deserving ascription of the divinity Anaxagoras effectively predicated of mind. Mind is in fact an attribute, not a substance at all. Hence no doubt the substitution of noēsis, ’intelligence’, for Anaxagoras’ nous.
Only air in a particular state has the power of intelligence; namely, when hotter than atmospheric air, but cooler than that in the vicinity of the sun (fr. 5). The surviving fragments say nothing of how air can take the form of, for example, earth or water (although the doxography speaks of compression; A1, A6 ). We might wonder why evidence that air pervades and controls everything should suggest that it is the basic substance. No doubt the underlying thought is simply that no substance could be dominant without being basic.
3 Psychology and physiology
If Diogenes conceived his chief general contribution to philosophy as rescuing Anaxagorean metaphysics from dualism, his work in psychology and physiology was, as noted, more influential. Diogenes’ systematic treatment of these topics challenges comparison with those of Anaxagoras and Empedocles. Following the argument given in fragment 2, he made sense perception a product of interaction between air within and air without (Theophrastus, On the Senses 39–45). His exposition began unusually but understandably with the best cases for his theory: smell and then hearing. A weaker explanation is provided for sight and taste however. Diogenes’ fanciful analysis of the vascular system allowed him to argue that air was conveyed by blood throughout the body to various destinations, including notably the head. Following Alcmaeon he conceived of the brain as the principal seat of sensations, which were apparently construed as functions of intelligence: Diogenes observed that when we have our minds on other things, we neither see nor hear. In general, the finer the air within and the more delicate the passages through which it is conveyed, the more acute the associated perceptions.
This explanatory scheme was applied to a great variety of phenomena. To take just one, pleasure is viewed as the result of efficient mixture of air and blood in the veins permeating the whole body. Many undesirable conditions are put down to the effect of moisture or ikmas. Evidently a key Diogenean notion, this was used to explain such phenomena as magnetism and the flooding of the Nile (A18, A33 ). Its action upon internal air inhibits intelligence, as manifested in sleep and drunkenness, and may also (to Aristophanes’ amusement) be evidenced in animals which breathe air close to the ground.
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