This also enables us to understand, what it is which recommends such and such aggregates, and not others, for classification. Those successions of objects, in which we are interested, determine the classifications which we form of them. Some successions are found to depend upon the clusters, called objects, all taken together. Thus a tree, a man, a stone, are the antecedents of certain consequents, as such; and not on account of any particular part of the cluster. Other consequents depend not upon the whole of the cluster, but upon some particular part: thus a tall tree, produces certain effects, which a tree not tall, cannot produce; a strong man, produces certain effects, which a man not strong cannot produce. When these consequents are so important, as to deserve particular attention, they and their antecedents must be marked. For this purpose, are employed the connotative terms marking differences. These terms enable us to group the clusters containing those antecedents into a sub-class; and NON-CONNOTATIVE or ABSTRACT terms, derived from them, enable {317} us to speak separately of that part of the cluster which we have to mark as the precise antecedent of the consequent which is engaging our attention. It is presumed, that these illustrations will suffice, to enable the reader to discern the real marking power of abstract terms, and also to perceive the mode of their formation. {318} CHAPTER X. MEMORY. "The science of metaphysics, as it regards the mind, is, in its most important respects, a science of analysis; and we carry on our analysis, only when we suspect that what is regarded by others as an ultimate principle, admits of still finer evolution into principles still more elementary."--_Inquiry into the Relation of Cause and Effect_, _by Thomas Brown, M.D._ P. iv. s. i. p. 331. IT has been already observed that if we had no other state of consciousness than sensation, we never could have any knowledge, excepting that of the present instant. The moment each of our sensations ceased, it would be gone, for ever; and we should be as if we had never been. The same would be the case if we had only ideas in addition to sensations. The sensation would be one state of consciousness, the idea another state of consciousness. But if they were perfectly insulated; the one having no connexion with the other; the idea, after the sensation, would give me no more information, than one sensation after another. We should still have the consciousness of the present instant, and nothing more. We should be wholly incapable of acquiring experience, and accommodating our actions {319} to the laws of nature. Of course we could not continue to exist.