We proceed afterwards to some clear and good additional remarks--p. 298. A class-term, as _black_, "is associated with two distinguishable things, but with the one much more than with the other: the clusters, with which it is associated, are variable: the peculiar sensation with which it is associated, is invariable. It is constantly, and therefore much more strongly, associated with the sensation, than with any of the clusters. It is at once a name of the clusters and a name of the sensation: but it is more peculiarly a name of the sensation." Again shortly afterwards, the abstract term is justly described as "marking exclusively one part (of the cluster), upon which such and such effects depend, no alteration being supposed in any other part of it."[p] [Footnote p: The abstract term is coined for the express purpose of marking one part of a cluster simultaneously present to the mind, and fixing attention upon it without the other parts--but the concrete term is often made to serve the same purpose, by means of the adverb quatenus, [Greek: ka/thoson, ê(=|] &c. These phrases are frequent both in Plato and Aristotle: the stock of abstract terms was in their day comparatively small. It is needless to multiply illustrations of that which pervades the compositions of both: a very good one appears in Plato, Republ. I., p. 340 D, 341 C, 342.] This process of marking exclusively, and attending to, one constant portion of a complex state of consciousness, amidst a {286} great variety of variable adjuncts--is doubtless one fundamental characteristic in Abstraction and Classification. A mystery was spread around it by Plato--first through his ascribing to the Constant a separate self-existence, apart from the Variables--still more by his hyperbolical predicates respecting these self-existent transcendental Entia. Plato[q] however in other passages gives many just opinions, respecting Classification, which are no way founded on Realism, and are equally admissible by Nominalists: and portions of Aristotle may be indicated, which describe the process of abstraction as clearly as any thing in Hobbes or Berkeley.[r]