The authorship of the fourth book is disputed. This is due partially to its content. It deals with an altogether different set of questions from the other three books, and is much more similar to
On Generation and Corruption. According to H. B. Gottschalk: Recently, its authenticity, or at the very least, its consistency with other Aristotelian texts, has been defended. Where exactly it should be placed in the corpus is another question.
Alexander placed it with GC (
On Generation and Corruption), but thought it was a different work from it.
Olympiodorus placed it between Cael. (
De Caelo, On the Heavens) and GC, while Patrizi placed it before
Parts of Animals. Only
Ammonius claims it is both genuine and in the right place. The fourth book consists of a detailed investigation of organic and natural processes, and attempts to explain the interaction and composition of elements by reference to the contrary physical qualities. It also provides a theory of secondary qualities, which emerge from different compositions of the primary qualities. This means that hardness or brittleness are due to the underlying relations between the primary contraries (hot, cold, dry, and moist). Chapter analysis: • Summary of the doctrine of four prime contraries (hot, cold, moist, dry) and their relation to the four elements (fire, air, water, earth). Hot and cold are the active factors responsible for generation and destruction. • Two and Three are an investigation of the effects of heat and cold on natural processes, in particular, concoction [πέψις]. Concoction is defined as the maturing process [τελέωσις] of a substance which initiates its own development by means of an inner heat, i.e. it is its own internal moving cause (379b18-25). The appropriate heat will "masters the indeterminacy" of the material elements, so as to give them form (380a1). Proper concoction is a sign of health (380a2). • Ripening is a specific kind of concoction [πέψις τις]: the process in which the nourishing elements in fruit attains maturity so that its seeds can produce life (380a11-15). Aristotle says we can speak metaphorically about other processes as maturation [τελέωσις], all processes in which "matter is determined by natural heat and cold" (280a18-22). The chapter then examines rawness as the antithesis of concoction: in-concoction of the nourishing element in fruit having indeterminate moisture (
380a27-b13). He then investigates related processes in which external influences effect the inner equilibrium of forces in natural compounds: boiling, scalding, and roasting. • Four through Nine are an investigation of the passive factors, moisture and dryness, and develop a systematic explanation of their secondary properties, the primary two being hard and soft. • Aristotle says that hard and soft are produced by processes of solidification or liquefaction that are due to heat and coldness. Drying is one kind of solidification. • Further investigation of solidification and liquefaction. (1) watery liquids, which are solidified by cold, liquefied by heat. (2) In mixtures of earth and water (which may also thicken instead of solidifying), either earth dominates, or, in which water dominates. • Discussion of particular examples: cheese, milk, blood, stones, wood, ebony, clay. Conclusion: anything that will solidify or thicken contains earth. • Summary of his theories of
hylomorphism and motion, as pertaining to the study of the physical properties of natural bodies. We are then given a list of the types of qualities that arise from the interactions between composite bodies. These are the effects of heat and cold on the passive components (moisture and dryness). The list is given in the form of a pair of opposites: "Capable or incapable of..." • Solidification or melting • Softening from heat or softening from cold • Bending or breaking • Fragmentation or impression • Plasticity or being squeezed • Ductility or malleability • Fissility or being cut • Viscosity or being compressed • Combustability or giving off fumes • Further investigation of the nature of solidification and softening. Examples: bronze, soda, salt, wool, grain. Then all 18 properties are investigated. • Discusses homoiomerous bodies and the effects of heat and cold on the processes of solidification and liquification. • Discusses examples (bronze, gold, silver, tin, iron, stone, flesh, bone sinew, skin, intestine, hair, fiber, veins) which are differentiated from non-homoiomerous bodies: everything composed of homoiomerous bodies, e.g. face, hand, foot, or wood, bark, leaf, root. • Discusses non-homoiomerous bodies. In the middle of the chapter he insists on the existence of functions [ἔργον] and purposes [ἕνεκα] in all natural processes, claiming they are only clearer in the case of living things like flesh, but no less present in inanimate nature (
390a17). Despite this insistence on final causality, the author goes on immediately to claim that all homoiomerous bodies can be produced by heat, cold, or their combination. The chapter ends the book by looking ahead to a further investigation of homoiomerous bodies (blood, flesh, semen, and the rest), which would lead into the study of non-homoiomerous, and then to bodies composed of them "such as humans, plants, and the like." (
390b24). ==See also==