The pragmatic value of organization is so conspicuously enforced in contemporary life that it hardly seems necessary to dwell upon the instrumental significance of classification and systematization. When the existence of qualitative and fixed species was denied to be the supreme object of knowledge, classification was often regarded, especially by the empirical school, as merely a linguistic device. It was convenient for memory and communication to have words that sum up a number of particulars. Classes were supposed to exist only in speech. Later, ideas were recognized as a kind of _tertium quid_ between things and words. Classes were allowed to exist in the mind as purely mental things. The critical disposition of empiricism is well exemplified here. To assign any objectivity to classes was to encourage a belief in eternal species and occult essences and to strengthen the arms of a decadent and obnoxious science--a point of view well illustrated in Locke. General _ideas_ are useful in economizing effort, enabling us to condense particular experiences into simpler and more easily carried bunches and making it easier to identify new observations. So far nominalism and conceptualism--the theory that kinds exist only in words or in ideas--was on the right track. It emphasized the teleological character of systems and classifications, that they exist for the sake of economy and efficiency in reaching ends. But this truth was perverted into a false notion, because the active and doing side of experience was denied or ignored. Concrete things have _ways_ of acting, as many ways of acting as they have points of interaction with other things. One thing is callous, unresponsive, inert in the presence of some other things; it is alert, eager, and on the aggressive with respect to other things; in a third case, it is receptive, docile. Now different ways of behaving, in spite of their endless diversity, may be classed together in view of common relationship to an end. No sensible person tries to do everything. He has certain main interests and leading aims by which he makes his behavior coherent and effective. To have an aim is to limit, select, concentrate, group. Thus a basis is furnished for selecting and organizing things according as their ways of acting are related to carrying forward pursuit. Cherry trees will be differently grouped by woodworkers, orchardists, artists, scientists and merry-makers. To the execution of different purposes different ways of acting and reacting on the part of trees are important. Each classification may be equally sound when the difference of ends is borne in mind.