Abstract

We have a basic definition of genus in Topics (I, 5, 102a31-35): ‘A genus is what is predicated in what a thing is of a number of things exhibiting differences in kind. We should treat as predicate in what a thing is all such things as it would be appropriate to mention in reply to the question “what is the object in question?”; as, for example, in the case of man, if asked that question, it is appropriate to say “He is an animal.”’ He indicates that ‘of the common predicates that which is most definitely predicated in what the thing is, is likely to be the genus.’ (To. , I, 18, ^108b22) From this definition, what is demonstrative in the definition of genus, Aristotle asserts, is ‘what is common to all the cases.’ (To., I, 18, ^108b22) This common thing is ‘one identical thing which is predicated of both and is differentiated in no merely accidental way.’ (Met., I, 1057b37) This means that the things in which the genus is common must be essentially different. In fact, this very common genus must be essentially different in the things it is their genus. Therefore, things that are identical in a genus are at the same time different in that very genus. This means that though the genus is the same in them, it is indeed different in them and they are not the same as each other in that very same genus but specifically different from each other: ‘For not only must the common nature attach to the different things, e.g. not only must both be animals, but this very animal must also be different for each (e.g. in the one case horse, in the other man), and therefore this common nature is specifically different for the two things (διὰ τοῦτο τὸ κοινὸν ἓτερον ἀλλήλων ἐστι τῷ εἴδει). One then will be in virtue of its own nature one sort of animal, and the other another, e.g. one a horse and the other a man. This difference then must be an otherness of the genus. For I give the name of ‘difference in the genus’ to an otherness which makes the genus itself other.’ A. Characteristics of genera The following are the characteristics of genera: 1. Those to which the same figure of predication applies are one in genus. (Met. , Δ, 1016b32-35) 2. Things that are one in genus are all one by analogy while things that are one by analogy are not all one in genus. (Met, Δ, 1016b35-1017a3) 3. A genus includes contraries. (Met., Δ, 1018a25-31) 4. All the intermediates are in the same genus as one another and as the things they stand between. (Met., I, 1057a18-30; 1057b31-34) 5. Not every predicate is a genus of what it is predicated on; for this would equate a genus with one of its own species. (PsA., A, 22, 83b7-10) 6. The opposite of the genus should always be the genus of the opposite. (To., Δ, 4, ^125a27-29) 7. A genus divides the object from other things. (To., Z, 3, 140a^24) 8. None of unity and being is a genus. (Met., B, 998b22-27; Met., K, 1059b31-34; PsA., B, 7, 92b12-14) 9. There is no necessity or even no possibility that things that are the same specifically or generically should be numerically the same. (To., H, I, 152b30-) 10. To be called one due to having one genus is in a way similar to be one due to having the same matter. (Met., Δ, 1016a24-28) 11. The substance of a thing involves its genus, and thereby all the higher genera are predicated of the lower. (To., Z, 5, 143a^20- ) 12. Being falls immediately into genera. (Met., Γ, 1004a4-6) 13. They do not exist apart from the individuals. (Met., B, 999a29-32; Met., I, 1053b21-22) 14. A genus is not a simple qualification but marks off the qualification of substance. (Cat., 5, 3b18-21) 15. Genera are criteria of difference when ‘the things have not their matter in common and are not generated out of each other.’ (Met., I, 1054b27-31) 16. The genus of a thing is its matter (ὓλη). (Met., I, 1058a23-25) 17. A genus is applicable to a wider range than its species. (Cat., 5, 3b21-23) 18. A genus is prior to its species in existence: while a genus reciprocates on the existence of its species, they do not reciprocate on the existence of their genus. (Cat., 13, 15a3- ) Aristotle’s example is this: if there is a fish there is an animal, but if there is an animal, there is not necessarily a fish. 19. The genus of a thing expresses ‘what it is’ and its essence. (To., I, 5, 102a31- ; To., Z, 5, 143a^20- ) 20. A genus is most familiar than its differentia and may be them all. (To., Z, 9, 149a16) 21. The genus is more substantial than its species. (Met., H, 1042a13-16) 22. One, being and substance cannot be classes. (Met., I, 1053b21-24; cf. 1054a8-11) 23. Aristotle draws a distinction between a simple and a composite concept in their falling within a genus. While a simple one can, a composite one cannot. He discusses this between ‘justice’ and ‘just man’: ‘the former falls within the genus, whereas the other does not … for nothing which does not happen to belong to the genus is essentially the genus; e.g. a white man is not essentially a color.’ (To., Γ, 1, ^116a24) 1) Genus and universal ‘Genera are universals’ (Met., Λ, 1069a26-27; Δ, 1014b9-10) and more universal than differentia and species (Met., Δ, 1014b9-12), but it is evident that not all universals are genera. (Met., A, 992b10-13) 2) Co-ordinate species The species resulting from the same division are co-ordinate species. They are the results of the same division in the same genus. Thus, none of them is prior or posterior to others but they are simultaneous by nature. (Cat., 13, 14b33-15a3) 3) Priority of genus to species Aristotle defines prior (λοιπόν) based on reciprocation as to implication of existence: ‘Τhat from which the implication of existence does not hold reciprocally is thought to be prior.’ (Cat., 12, 14a32-34) His examples are genera and species: ‘genera are always prior to species since they do not reciprocate as to implication of existence.’ (Cat., 13, 15a4-6) Τhus, if there is a fish, there is an animal, but if there is an animal, there is not necessarily a fish. 4) Generic versus non-generic attributes As the above discussions illustrates, not all attributes can be genera of their subjects. Thus, we ought to distinguish between generic and non-generic attributes of each subject. K. J. Spalding distinguishes between substantive and classificatory attributes, a distinction that, he believes, is absent from the Aristotelian logic. Classificatory attributes are those that originate and exist in class alone, and are generic like ‘human’ and ‘animal.’ These attributes do not belong to the individual as individual. For example, animal belongs to the Socrates not as Socrates but as man. Substantive attributes, on the other hand, are those that belong to Socrates as Socrates and not as a class. Attributes like sense attributes that originate independently of generic structure and ‘do not involve a necessary relation to or dependence on a class’ are substantive attributes.