Aristotle's Theory Unity of Science

11 Introductioncan prove that wing is predicated of bird by using the proper principlesof the subject genus, bird; similarly with the fish's fin' In spite of theindependence and autonomy of the demonstrations, there is a parallel inthe proofs, an analogical identity of relation: as wing is to bird, so fin is tofish. This identity, however, cannot be abstracted from, and must always beper se related to, the subject-genera in which the demonstrations take place.This is a result of the fact that the subjects, bird and fish, determine thequa level at which the attributes and causes are treated. At the same time,behind the generic difference there is the intimation of a more abstractsubject-genus to which both bird and fish are related. This subject-genusarises from the fact that flying and swimming are forms of locomotion,and that wing and fin are instrumental parts of locomotion. The secondand third chapters of this book will be devoted to explaining how analogyfacilitates this limited degree of unity among different scientific subjects.The second object of our investigation, the focal relationship, is amethod for drawing together in a single subject matter objects that areof different genera lO According to Aristotle's favourite example, the term'medical' applies to many different kinds of objects. For instance, we callan operation medical, a doctor medical, a scalpel medical, not because theypossess the same attribute, medical, but because they are all related to thething that is called medical in the primary sense, the medical art. The othermedical things are so called because they are the work of the medical art,the possessor of the medical art, or the instrument of the medical art. Thedefinitions of these derivatively medical things contain in themselves theprimary term or its definition. Chapter 4 will be devoted to analysing thefocal relationship in terms of -Aristotle's theory of science and showingthat medical is predicated of the derivative medical things in virtue of avariety of per se relations. Although all the medical objects do not form asingle genus, in the sense that they are not of the same kind or similar toone another, the definitional relations among them show how they forma genus in another important sense of the term, objects related by per seconnections to a single subject-genus.9 This is Aristotle's standard pattern of demonstration in the PA . We perceive that a birdhas wings from obseJVation, but to know in the fullest sense we must know why, andthis knowledge comes from relating the cause to the fact in a demonstration. We cannotprove that a bird has wings from observation, because only demonstration providesproof.10 G.E.L. Owen (1960) first provided the current English translation of 7rpor tV A.EyOP.EVOVas 'focal meaning.' It is also known as 'relational equivocity.' Most recently Shields1999 has called this (as well as cumulation) 'core dependent homonymy.'