Nevertheless, those who read with attention Locke's admirably clear pages must notice that he does not succeed in really setting to rest the doubt that has suggested itself. It becomes clear that Locke felt so sure of the existence of the external world because he now and then slipped into the inconsistent doctrine that he perceived it immediately, and not merely through his ideas. Are those things "which he sees and feels" _external_ things? Does he see and feel them directly, or must he infer from his ideas that he sees and feels them? If the latter, why may one not still doubt? Evidently the appeal is to a direct experience of material things, and Locke has forgotten that he must be a Lockian. "I have often remarked, in many instances," writes Descartes, "that there is a great difference between an object and its idea." How could the man possibly have remarked this, when he had never in his life perceived the object corresponding to any idea, but had been altogether shut up to ideas? "Thus I see, whilst I write this," says Locke,[1] "I can change the appearance of the paper, and by designing the letters tell beforehand what new idea it shall exhibit the very next moment, by barely drawing my pen over it, which will neither appear (let me fancy as much as I will), if my hand stands still, or though I move my pen, if my eyes be shut; nor, when those characters are once made on the paper, can I choose afterward but see them as they are; that is, have the ideas of such letters as I have made. Whence it is manifest, that they are not barely the sport and play of my own imagination, when I find that the characters that were made at the pleasure of my own thought do not obey them; nor yet cease to be, whenever I shall fancy it; but continue to affect the senses constantly and regularly, according to the figures I made them." 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.