Plotinos: Complete Works, v. 3 In Chronological Order,...

This is by what we must begin. Having to speak of sense-objects, and knowing that all of them are contained in this world here below, we must first scrutinize this world, establish within it divisions according to the nature of the (beings) which compose it, and then distribute them into genera, just as we would do if we had to analyze the voice whose nature is infinite (by the diversity of sounds it produces), reducing it to a definite number of kinds.344 Observing the elements common to many sounds, we would reduce them to one unity, then, to a superior unity, further to a supreme unity, in which these sounds appear as a small number of classes. Then, the elements common to these individuals would be called "species," and that common to various species would be called a genus. As to the voice, it is easy enough to discover each species, to reduce all the species to unity, and to predicate of all of them (as highest genus or category) the general element, the voice. But an analysis as summary as this is impossible with the (more complicated universe). In the sense-world we will have to recognize several genera, which will differ from those of the intelligible world, since the sense-world itself differs from the intelligible world so much that it is not its counterpart, but only its image, whose only element common (to its model) is the name.