Aristotle's Theory Unity of Science

9 Introductioncannot all be included in one universal science. Each science has a subject ora subject-genus. This is what the science is about and the subject of whichthe predicates are predicated. A science is the sum of the demonstrativesyllogisms that concern the same subject.' The subject of the science isindicated by the qua expression, and the per se criterion for includingother terms in a science implies that each science is autonomous and hasits own and unique set of principles.When these restrictions are violated, when there is an attempt tointroduce a term that is not per se and qua related to the other termsinto a demonstrative syllogism, the result is an error, which Aristotle callsI'ETa/3arJ'lS or kind-crossing, and this will destroy the demonstrative powerof the syllogism and the cogency of the science.In contrast to Plato's and Speusippus' universalizing and inclusivetendencies, Aristotle's theory of demonstration is a powerfully isolatingforce. The qua requirement especially entails that understanding occurswithin a single subject-genus, and not in relation to other genera throughan analysis of sameness and difference.' Each science will be specializedand isolated from every other except by incidental connections, and therewill be no communication between disciplines. Each subject-genus, boundby necessity solely to its own principles and predicates, will form an islandin the sea of Being. The view of the world that this theory of sciencerepresents will be that of a heap of subjects, in which one genus is onlyincidentally related to another.It is clear, however, that Aristotle never advocated such a degree ofisolation. In fact there are a multitude of ways in which sciences are connectedwith one another and share principles. The axioms, like the principleof non-contradiction, are common to all sciences, and are the preconditionfor any understanding at all. More elaborately developed within the APois the connection between a more abstract, superordinate science and a lessabstract, subordinate science. A superordinate science, usually a branch ofmathematics, supplies principles and explanations for a fact or conclusionfound in a distinct and subordinate natural science, for instance, harmonicsor optics. Since this technique and its place in the APo has been well studied6 I am deliberate in avoiding the claim that a science is the sum of demonstrations whichhave the same minor term for reasons which will be discussed in chapter 4.7 No doubt, division remains an important part of Aristotle's epistemology, but it plays apreliminary role in establishing the extent of the subject-genera and the attributes thatare coextensive with them. It is not the primary form of understanding. See Ferejohn1991, who places division in the 'framing' or pre-demonstrative stage of science. Seealso chapter 2 below.