Page - 249 - in The Complete Aristotle

of knowledge. For the genera of relatives ought themselves also to be relatives, as is the case with ‘double’: for multiple’, which is the genus of ‘double’, is itself also a relative. To speak generally, the genus ought to fall under the same division as the species: for if the species be a substance, so too should be the genus, and if the species be a quality, so too the genus should be a quality; e.g. if white be a quality, so too should colour be. Likewise, also, in other cases. Again, see whether it be necessary or possible for the genus to partake of the object which has been placed in the genus. ‘To partake’ is defined as ‘to admit the definition of that which is partaken. Clearly, therefore, the species partake of the genera, but not the genera of the species: for the species admits the definition of the genus, whereas the genus does not admit that of the species. You must look, therefore, and see whether the genus rendered partakes or can possibly partake of the species, e.g. if any one were to render anything as genus of ‘being’ or of ‘unity’: for then the result will be that the genus partakes of the species: for of everything that is, ‘being’ and ‘unity’ are predicated, and therefore their definition as well. Moreover, see if there be anything of which the species rendered is true, while the genus is not so, e.g. supposing ‘being’ or ‘object of knowledge’ were stated to be the genus of ‘object of opinion’. For ‘object of opinion’ will be a predicate of what does not exist; for many things which do not exist are objects of opinion; whereas that ‘being’ or ‘object of knowledge’ is not predicated of what does not exist is clear. So that neither ‘being’ nor ‘object of knowledge’ is the genus of ‘object of opinion’: for of the objects of which the species is predicated, the genus ought to be predicated as well. Again, see whether the object placed in the genus be quite unable to partake of any of its species: for it is impossible that it should partake of the genus if it do not partake of any of its species, except it be one of the species reached by the first division: these do partake of the genus alone. If, therefore, ‘Motion’ be stated as the genus of pleasure, you should look and see if pleasure be neither locomotion nor alteration, nor any of the rest of the given modes of motion: for clearly you may then take it that it does not partake of any of the species, and therefore not of the genus either, since what partakes of the genus must necessarily partake of one of the species as well: so that pleasure could not be a species of Motion, nor yet be one of the individual phenomena comprised under the term ‘motion’. For individuals as well partake in the genus and the species, as (e.g.) an individual man partakes of both ‘man’ and ‘animal’. Moreover, see if the term placed in the genus has a wider denotation than the genus, as (e.g.) ‘object of opinion’ has, as compared with ‘being’: for both 249