But when we begin to consider this view more closely, all sorts of difficulties arise. We have already seen that, on grounds derived from physics, the table itself, as a physical thing, cannot be regarded as the object of our perception, if the object is something essential to the existence of the perception. In suitable circumstances, we shall have the same perception although there is no table. In fact, there is no event outside the brain which _must_ exist whenever we “see a table”. It seems preposterous to say that when we think we see a table we really see a motion in our own brain. Hence we are led to the conclusion that the “object” which is essential to the existence of an act of perception is just as “mental” as the perceiving. In fact, so this theory runs, the mental occurrence called “perceiving” is one which contains within itself the relation of perceiver and perceived, both sides of the relation being equally “mental”. Now, however, there seems no longer any reason to suppose that there is any essentially relational character about what occurs in us when we perceive. The original reason for thinking so was the naively realistic view that we see the actual table. If what we see is as mental as our seeing, why distinguish between the two? The coloured pattern that we see is not really “out there”, as we had supposed; it is in our heads, if we are speaking of physical space. True, more than a coloured pattern occurs when we “see a table”. There are tactual expectations or images: there is probably belief in an external object; and afterwards there may be memory or other “mnemic” effects. All this may be taken as representing what the above theory took to be the “subject” side of an act of perception, while the coloured pattern is what the theory took to be the “object” side. But both sides are on a level as regards being “mental”. And the relation between the two sides is not of such a kind that the existence of the one logically demands the existence of the other; on the contrary, the relation between the two sides is causal, being dependent upon experience and the law of association.