Aristotele e il cervello: Le teorie del più grande biologo dell’ antichità nella storia del pensiero scientifico (review)

In Aristotle’s natural philosophy, the heart is the source of the basic vital functions in higher organisms. As such, it is the seat of the vegetative and sensitive soul, and of their main instruments, in other words, innate heat and spirit (pneuma). Aristotle argued that all sense and life organs communicated with the heart—and not with the brain—through an elaborate system of channels (poroi) and blood vessels (phlebes). In addition, he closely linked the tendons (neura), seen as fibers originating from the most peripheral ramifications of the arteries, to the heart. In this way, he made the heart the source of animal motion, assisted by the spirits with their inherent ability to contract and expand. In this anatomical picture, the brain was left with the still-important function of regulating the temperature of the body. The heat of the heart was purported to be so intense that the supposedly refrigerating and ventilating functions performed by the lungs during respiration were not sufficient to moderate it. For this reason, Aristotle assumed that the brain provided a source of extra cooling due to the constitutively cold and moist nature of its temperament. The process of sleep, in particular, was meant to cool the blood and the spirits coming from the heart. Finally, the brain’s function of thermoregulation was further facilitated by the sutures, the serrated articulations of the skull.

This, in a nutshell, is the role of the brain in Aristotle’s anatomy, a subject on which Tullio Manzoni has now devoted a book that has the merit of being factually accurate and stylistically clear. Manzoni’s expertise in the field of neurophysiology places him in the enviable position of being able to compare past and present anatomical beliefs in full cognition of the facts. His knowledge of the technical terminology is impeccable, and his analysis of Aristotle’s views is supported by constant references to ancient and medieval commentators, Renaissance humanists, and anatomists. The problem with the book, though, does not lie in the amount of information displayed by the author but in his assumptions concerning history and epistemology. No doubt, some might object that there is no point in getting antsy about philosophical or even methodological quibbles when the author’s aim is simply to produce a work of history. I then reply with the trivial assumption that any historical account, however neutral it is in presentation, contains in fact a definite view of history and scientific progress. Already, in the introduction to the book, Manzoni passes a very severe judgment on Aristotle’s science. He distinguishes between anatomical notions based on empirical observations and other notions that often “are not derived from empirical observations.” The former, although they did not stand the test of time, nevertheless have some foundation in controllable experience; the latter “could not help being seen from the very beginning as absurd and naive popular beliefs” (p. 16). “Absurd” and “naive” are strong words, and the domain of supposedly irrational and unfounded beliefs is a treacherous territory to enter when relying too confidently on the benefit of hindsight. It is often difficult to assess who is really superstitious in the end. The following, for instance, are some of Manzoni’s own methodological and epistemological superstitions:

The notion of temperament or complexion was “a long-lasting medical doctrine” that, in fact, was “based on nothing” (p. 33). More specifically, the question of the temperament of the brain is “completely meaningless for modern medicine”

(p. 153).

The theory of the faculties of the mind localized in the ventricles of the brain rests on “a logic that today appears absurd”

(p. 39).

Finalism led Aristotle to teleological explanations concerning the functions of the organs that are “either banal or ridiculous”

(p. 102).

Aristotle’s explanation of the mechanism of respiration...