Rationalism of Spinoza and Leibniz

Furthermore, among simple ideas of sensation, Locke made the distinction between ideas of primary and ideas of secondary qualities. The former are resemblances or copies of the actual properties of things ; the ideas we have of the extension, figure, texture and motion of the parts of things accurately represent the nature of the things that give rise to them. The latter are not resemblances of any characteristics possessed by things them selves, but are effects produced, through the operation upon our senses, of powers which things possess by reason of their primary qualities.

Locke and "Ideas..

"Ideas" had for Locke, as they had for Descartes, a two-fold aspect. They on the one hand, an immediate aspect, inasmuch as they were themselves the direct objects of our apprehension; they had, on the other hand, a representative aspect, inasmuch as it was through them that we come to know real things, such "things" being distinct from "ideas." It is in reference to this latter aspect that the crucial difficulties of Locke's theory evince themselves. How far can we ever be assured that by sensation we have a knowledge of things? Seeing that any comparison of sense ideas with real things is precluded, we cannot have that intuitive certainty con cerning the latter which Locke thinks we have of the existence of self, nor that demonstrative certainty which he thinks we have of the existence of God. And he has to admit that what we have here is only entitled to be called "assurance" rather than knowl edge,—assurance which approaches knowledge in proportion as the "ideas" concerned are perfectly simple, as is the case with the ideas of simple sense qualities, more particularly of those called primary. The difficulty comes to a head in the account he has to give of the idea of "substance." Since this idea could not have been obtained by sensation or reflection, Locke was com pelled to ascribe it to the workmanship of the mind, and he did so without considering apparently the consequences which would have ensued had he remained faithful to his dictum that what soever was thus added to the given ideas of sense or reflection was ideal only and to be allowed no share in determining the content of the real.

Berkeley.

The line of thought by which Berkeley (1685– '753) reached the fundamental principle of his own theory of knowledge took its rise from reflection upon the dubious function in the development of experience attributed in the Essay to material substances. In arguing that to call in the powers of matter as the originating causes of the occurrence of "ideas" was to have recourse to an occult mode of activity, Berkeley was reverting to a line of argument which the Cartesians had made familiar.

But in the light of Locke's investigation, he was convinced that he could push his way further. Locke had maintained that the range of our knowledge did not extend beyond the range of our "ideas"; and had, at the same time, not only detected in knowl edge a reference to "things" other than "ideas" but had intro duced into his catalogue of ideas those called abstract, which were confessedly devoid of the characteristics of "ideas" as supplied by sense or reflection. Indeed, in both the ordinary and the scientific notion of external things, Berkeley discerned a striking illustration of the result of attempting to carry out the illusory process of abstraction. For these external things were supposed to have somehow a place in the world of perceived reality, and yet to be of such a nature as to preclude the possibility of their being perceived. There is first withdrawn from them every characteristic necessary to constitute them possible objects of experience, and then they are still spoken of as though they did form part of our experience. Locke would have repudiated the doctrine of univer salia ante rem, but what he actually meant by such terms as "matter," "substance," and the like were just universals of this description, i.e., hypostatised abstractions. Berkeley's polemic against "abstract ideas" was intended, therefore, to prepare the way for his own construction. Although discarding Locke's doc trine of abstraction, he recognises that generalisation is indis pensable for knowledge and for communication of knowledge.

Locke had not ignored, but had certainly not done justice to, the function that accrues to an "idea" in virtue of its being representative of other "ideas"; and it is this function upon which Berkeley fastens in the present connection. "An idea which, con sidered in itself is particular, becomes general by being made to represent or stand for all other particular ideas of the same sort." It must be confessed, however, that important though the relation of sign and that which is signified is in the development of knowledge, it will not bear the weight that Berkeley here reposes upon it, for the "sort" or species must in some way have been already determined before any particular idea could "stand for" or "represent" it.