Locke is as bad as Descartes.  Evidently he regards himself as able to turn to the external world and perceive the relation that things hold to ideas.  Such an inconsistency may escape the writer who has been guilty of it, but it is not likely to escape the notice of all those who come after him.  Some one is sure to draw the consequences of a doctrine more rigorously, and to come to conclusions, it may be, very unpalatable to the man who propounded the doctrine in the first instance.

The type of doctrine represented by Descartes and Locke is that of Representative Perception.  It holds that we know real external things only through their mental representatives.  It has also been called Hypothetical Realism, because it accepts the existence of a real world, but bases our knowledge of it upon an inference from our sensations or ideas.

49.  THE STEP TO IDEALISM.—­The admirable clearness with which Locke writes makes it the easier for his reader to detect the untenability of his position.  He uses simple language, and he never takes refuge in vague and ambiguous phrases.  When he tells us that the mind is wholly shut up to its ideas, and then later assumes that it is not shut up to its ideas, but can perceive external things, we see plainly that there must be a blunder somewhere.

George Berkeley (1684-1753), Bishop of Cloyne, followed out more rigorously the consequences to be deduced from the assumption that all our direct knowledge is of ideas; and in a youthful work of the highest genius entitled “The Principles of Human Knowledge,” he maintained that there is no material world at all.

When we examine with care the objects of sense, the “things” which present themselves to us, he argues, we find that they resolve themselves into sensations, or “ideas of sense.”  What can we mean by the word “apple,” if we do not mean the group of experiences in which alone an apple is presented to us?  The word is nothing else than a name for this group as a group.  Take away the color, the hardness, the odor, the taste; what have we left?  And color, hardness, odor, taste, and anything else that may be referred to any object as a quality, can exist, he claims, only in a perceiving mind; for such things are nothing else than sensations, and how can there be an unperceived sensation?

The things which we perceive, then, he calls complexes of ideas.  Have we any reason to believe that these ideas, which exist in the mind, are to be accepted as representatives of things of a different kind, which are not mental at all?  Not a shadow of a reason, says Berkeley; there is simply no basis for inference at all, and we cannot even make clear what it is that we are setting out to infer under the name of matter.  We need not, therefore, grieve over the loss of the material world, for we have suffered no loss; one cannot lose what one has never had.

Thus, the objects of human knowledge, the only things of which it means anything to speak, are:  (1) Ideas of Sense; (2) Ideas of Memory and Imagination; (3) The Passions and Operations of the Mind; and (4) The Self that perceives all These.