These are the prominent thoughts in the Lockian philosophy. Its empiricism is clear as day. The mind, according to it, is in itself bare, and only a mirror of the outer world,—a dark space which passively receives the images of external objects; its whole content is made by the impressions furnished it by material things. _Nihil est in intellectu, quod non fuerit in sensu_—is the watchword of this standpoint. While Locke, by this proposition, expresses the undoubted preponderance of the material over the intellectual, he does so still more decisively when he declares that it is possible and even probable that the mind is a material essence. He does not admit the reverse possibility, that material things may be classed under the intellectual as a special kind. Hence with him mind is the secondary to matter, and hence he is seen to take the characteristic standpoint of realism (_cf._ § XXVII). It is true that Locke was not always logically consistent, and in many points did not thoroughly carry out his empiricism: but we can clearly see that the road which will be taken in the farther development of this direction, will result in a thorough denial of the ideal factor.
The empiricism of Locke, wholly national as it is, soon became the ruling philosophy in England. Standing on its basis we find _Isaac Newton_, the great mathematician (1642-1727), _Samuel Clarke_, a disciple of Newton, whose chief attention was given to moral philosophy (1675-1729), the English moralists of this period, _William Wollaston_ (1659-1724), the Earl of _Shaftesbury_ (1671-1713), _Francis Hutcheson_ (1694-1746), and even some opponents of Locke, as _Peter Brown_, who died 1735.
As already remarked, Locke had not been wholly consistent with the standpoint of empiricism. Though conceding to material objects a decided superiority above the thinking subject, there was yet one point, viz., the recognition of substance, where he claimed for the thinking a power above the objective world. Among all the complex ideas which are formed by the subjective thinking, the idea of substance is, according to Locke, the only one which has objective reality; all the rest being purely subjective, with nothing actually corresponding to them in the objective world. But in the very fact that the subjective thinking places the conception of substance, which it has formed, in the objective world, it affirms an objective relation of things, an objective connection of them among each other, and an existing rationality. The reason of the subject in this respect stands in a certain degree above the objective world, for the relation of substance is not derived immediately from the world of sense, and is no product of sensation nor of perception through the sense. On a pure empirical standpoint—and such was Locke’s—it was therefore illogical to allow the conception of substance to remain possessed of objective being. If the understanding is essentially a bare and empty space, a white unwritten paper, if its whole content of objective knowledge consists in the impressions made upon it by material things, then must the conception of substance also be explained as a mere subjective notion, a union of ideas joined together at the mind’s pleasure, and the subject itself, thus fully deprived of every thing to which it could lay claim, must become wholly subordinated to the material world. This stride to a logical empiricism Hume has made in his criticism on the conception of causality.