hypothetical necessity: if an animal is to discharge a certain function, it must have such
and such a material constitution. Aristotle arranges his subjects as in the History: animal
groups that belong together, e.g. birds, fish, are treated together; parts common to many
groups (especially internal organs) are treated together and given single explanations.
Broadly Aristotle moves from highest life form to lowest, from most general to most spe-
cific, and from the head down. He rejects the dichotomous form of division popular in the
Academy in favor of a system of multiple differentiae, e.g. birds have several general
essential features in which they vary from one another by having more or less (longer/
shorter beaks).
Finally (apart from spurious works) the Generation of Animals investigates the material and
efficient cause, though final and formal play subsidiary roles. Differences among sexual
organs, modes of propagation and causes of the differences among animal groups are
treated in the manner of the Parts. In procreation the male semen, a concoction of blood,
provides the form and efficient cause; female menstrual fluid provides the matter. Imperfect
mastering of the menstrual fluid by the semen results in a female offspring. Resemblances to
other relatives on the mother’s side and father’s occur by “relapse.” Aristotle refutes the
theory of pangenesis, according to which the seed is gathered from and composed of all
parts of the body. Lower animal forms, including testacea, are generated spontaneously by
the vital heat present in the air forming a kind of froth in mud. Finally, some parts and
qualities (e.g. eye color) are not for a purpose, but have a material cause.
Ed.: I. Bekker, Aristotelis Opera (1831); Oxford Classical Texts for Physics, de Caelo, de Anima; H. Joachim,
de Generatione et Corruptione (1926); F.H. Fobes, Meteorologica (1919); Loeb for biological works.
Trans.: The Complete Works of Aristotle, ed. J. Barnes (1984).
Studies: DSB 1.250–281, G.E.L. Owen et al.; G. Freudenthal, Aristotle’s Theory of Material Substance
(1995); L. Judson, Aristotle’s Physics (1991); J.G. Lennox, Aristotle’s Philosophy of Biology (2001); Fr.
Solmsen, Aristotle’s System of the Physical World (1960); NDSB 1.99–107, J.G. Lennox.
Malcolm C. Wilson
Aristotelian Corpus On Breath (ca 270 – 230 BCE)
The short Pseudo-Aristotelian treatise On Breath (481a1–486b4) is commonly believed to be
a product of the mid-3rd c. Peripatos. Some have connected it with T,
S L and E.
The treatise starts by investigating the preservation of the innate breath (emphuton
pneuma) and its increase (§ 1 – 2), polemizes by name against A (§2), and dis-
cusses various physiological questions all in some way connected with the function of
pneuma. The author treats respiration (§3), alluding (482a28–31) to A On Respir-
ation 1 (470b6–9), movement of pneuma through the vessels (§ 4 – 6), nature and functions
of the bones (§ 7), locomotion (§8), and the function of heat in biological processes (§9).
Jaeger considers §9 a later Stoic polemic against Strato ̄n; Roselli defends it as part of
the original work.
The author very rarely gives solutions to the problems presented to the reader. The
aporetic nature of the discussion, combined with its brevity and the corrupt status of the
text, makes On Breath a rather difficult text. It may be interpreted as a Peripatetic
reaction to 3rd c. medical discoveries. The author refers clearly to Erasistratos’ theory of
skin composition (483b5–19), but elsewhere the unnamed referent is difficult to
determine.
ARISTOTELIAN CORPUS ON BREATH