The Introduction to the _Principles_ is a proclamation of war against “abstract ideas,” which is renewed in the body of the work, and again more than once in the writings of Berkeley’s early and middle life, but is significantly withdrawn in his old age. In the ardour of youth, his prime remedy for anarchy in philosophy, and for the sceptical disposition which philosophy had been apt to generate, was suppression of abstract ideas as impossible ideas—empty names heedlessly accepted as ideas—an evil to be counteracted by steady adherence to the concrete experience found in our senses and inner consciousness. Never to lose our hold of positive facts, and always to individualise general conceptions, are regulative maxims by which Berkeley would make us govern our investigation of ultimate problems. He takes up his position in the actual universe of applied reason; not in the empty void of abstract reason, remote from particulars and succession of change, in which no real existence is found. All realisable ideas must be either concrete data of sense, or concrete data of inward consciousness. It is relations embodied in particular facts, not pretended abstract ideas, that give fruitful meaning to common terms. Abstract matter, abstract substance, abstract power, abstract space, abstract time—unindividualisable in sense or in imagination—must all be void of meaning; the issue of unlawful analysis, which pretends to find what is real without the concrete ideas that make the real, because percipient spirit is the indispensable factor of all reality. The only lawful abstraction is _nominal_—the application, that is to say, of a name in common to an indefinite number of things which resemble one another. This is Berkeley’s “Nominalism.” Berkeley takes Locke as the representative advocate of the “abstract ideas” against which he wages war in the Introduction to the _Principles_. Under cover of an ambiguity in the term _idea_, he is unconsciously fighting against a man of straw. He supposes that Locke means by _idea_ only a concrete datum of sense, or of imagination; and he argues that we cannot without contradiction abstract from all such data, and yet retain idea. But Locke includes among _his_ ideas intellectual relations—what Berkeley himself afterwards distinguished as _notions_, in contrast with ideas. This polemic against Locke is therefore one of verbal confusion. In later life he probably saw this, as he saw deeper into the whole question involved. This is suggested by the omission of the argument against abstract ideas, given in earlier editions of _Alciphron_, from the edition published a year before he died. In his juvenile attack on abstractions, his characteristic impetuosity seems to carry him to the extreme of rejecting rational relations that are involved in the objectivity of sensible things and natural order, thus resting experience at last only on phenomena—particular and contingent.