works) is very impressive; but his human anatomy is vitiated by the fact that he was rarely, if
ever, able to dissect human cadavers (a fact he laments: he recommends the novice anato-
mist to take advantage of any lucky chance, such as the fortuitous exposure of a riparian
graveyard by flooding, to gain knowledge of the human skeleton). Consequently his human
anatomy relies on inference from comparison with primates and other mammals, which he
both dissected and vivisected to uncover inner workings and determine particular functions
of parts (such as the recurrent laryngeal nerve). All of this knowledge contributed to his
boundless admiration for nature’s technical skill, which in turn informs his powerful natural
teleology: no-one versed in anatomy can seriously doubt that animals’ parts are providen-
tially constructed, ordered and arranged, a faith most clearly expounded in On the Function of
the Parts, but evident elsewhere as well.
This teleological bent makes him unremittingly hostile to atomism (although he also
considers atomism, as a sort of monism, to have been refuted by Hippokrate ̄s’ Nature of
Man (s.v. H C): nothing which did not involve qualitative intermixture
could feel pain; we do feel pain, so we involve qualitative intermixture). Equally, he is hostile
to what he sees (rightly) as the excessively reductionistic mechanism of the atomists in
philosophy, and their medical counterparts, in particular E and A-
. Mere mechanical principles such as that of horror vacui cannot on their own account
for the fluid dynamics of the body; and this, as well as the falsity of other Erasistratean
views, such as that the arteries in their normal condition contain no blood, can be shown by
experience and reason. Rather we must posit (although not as a scientific last word: this is
merely the beginning of the account) the existence of certain natural powers (attraction,
retention, alteration, expulsion) possessed by the various parts of the body (the kidneys
naturally attract urine, for instance: On the Natural Powers). His great avowed philosophical
debt is to P, a debt he details in On the Doctrines of Hippokrate ̄s and Plato (often cited as
PHP), a long work which seeks to show that in all important respects his two great author-
ities were in agreement, not just about physics, but also about the nature of the soul, which
Gale ̄n views, contra the Stoics, as being demonstrably tripartite, although he is notably and
consistently agnostic when it comes to its actual nature, refusing to commit himself to
Platonic immaterialism. His overall teleology is also Platonic (the marvelous complexity
and adaptiveness of biological structures is clear evidence, he thinks, of intelligent design),
although the fine details owe more, as he acknowledges, to Aristotle (with whom he disagrees
on important points, however, rejecting cardiocentric psychology on the basis of neuro-
logical investigation, and ridiculing the notion that the female contributes no developed
form in generation: On Semen).
In the end, Gale ̄n’s system is powerful, synthetic, but not crudely eclectic. It allows for
both reason and experience; and it is optimistic – excessively so – about its ability to deliver
theoretical and practical knowledge. Its obvious methodological strengths (insistence on
logic, empirical testing, the ultimate criterial role of the senses) are undercut by evident
shortcomings, notably Gale ̄n’s unduly sanguine belief that he has, in fact, provided solid,
irrefutable demonstrations of physical hypotheses (such as four-quality and four-humor
theory). Yet he is also capable of caution; he repeatedly notes that, while he has shown that
the origin of voluntary motion and the receptor of sensation is the brain and that these
psychological faculties are mediated by the nervous system, the actual nature of the soul is
unknown. Evidence clearly shows it to be susceptible to material effects (The Powers of the
Soul follow the Mixtures of the Body), suggesting that materialism is true; but he cannot rule out
the possibility of Plato being right after all about the soul’s immateriality.
GALE ̄N OF PERGAMON