In the case of the seen light,[60] reference to the velocity of light is quite adequate to account for its time and space differences from the star. But viewed as a case of what is known (on the supposition that perception is knowing), reference to it only increases the contrast between the real object and the object known in perception. For, being just as much a part of the object that causes the perception as is the star itself, it (the velocity of light) _ought_ logically to be part of what is known in the perception, while it is not. Since the velocity of light is a constituent element in the star, it should be known in the perception; since it is not so known, reference to it only increases the discrepancy between the object of the perception--the seen light--and the real, astronomical star. The same is true of any physical condition that might be referred to: _The very things that, from the standpoint of perception as a natural event, are conditions that account for its happening are, from the standpoint of perception as a case of knowledge, part of the object which, if knowledge is to be valid, ought to be known, but is not._ In this fact we have, perhaps, the ground of the idealist's disregard of the oft-proffered physical explanation of the difference between the perceptual event and _the_ (so-called) real object. And it is quite possible that some realists who read these lines will feel that in my last paragraphs I have been making a covert argument for idealism. Not so, I repeat; they are an argument for a truly naïve realism. The presentative realist, in his appeal to "common-sense" and the "plain man," first sophisticates the umpire and then appeals. He stops a good way short of a genuine naïveté. The plain man, for a surety, does not regard noises heard, lights seen, etc., as mental existences; but neither does he regard them as things _known_. That they are just things is good enough for him. That they are in relation to mind, or in relation to mind as their "knower," no more occurs to him than that they are mental. By this I mean much more than that the formulae of epistemology are foreign to him; I mean that his attitude to these things _as_ things involves their _not_ being in relation to him as a mind or a knower. He is in the attitude of a liker or hater, a doer or an appreciator. When he takes the attitude of a knower he begins to inquire. Once depart from thorough naïveté, and substitute for it the psychological theory that perception is a cognitive presentation to a mind of a causal object, and the first step is taken on the road which ends in an idealistic system. III