Nevertheless, the tendency to think that the only object or, at least, the only direct object of the mind is something mental still requires explanation. It seems due to a tendency to treat self-consciousness as similar to consciousness of the world. When in reflection we turn our attention away from the world to the activity by which we come to know it, we tend to think of our knowledge of the world as a reality to be apprehended similar to the world which we apprehended prior to reflection. We thereby implicitly treat this knowledge as something which, like the world, merely _is_ and is not the knowledge of anything; in other words, we imply that, so far from being knowledge, i. e. the knowing of a reality, it is precisely that which we distinguish from knowledge, viz. a reality to be known, although--since knowledge must be mental--we imply that it is a reality of the special kind called mental. But if the knowledge upon which we reflect is thus treated as consisting in a mental reality which merely _is_, it is implied that in this knowledge the world is not, at any rate directly, object of the mind, for _ex hypothesi_ a reality which merely _is_ and is not the knowledge of anything has no object. Hence it comes to be thought that the only object or, at least, the only direct object of the mind is this mental reality itself, which is the object of reflection; in other words, that the only immediate object of the mind comes to be thought of as its own idea. The root of the mistake lies in the initial supposition--which, it may be noted, seems to underlie the whole treatment of knowledge by empirical psychology--that knowledge can be treated as a reality to be apprehended, in the way in which any reality which is not knowledge is a reality to be apprehended. We may now revert to that form of idealism which maintains that the essential relation of reality to the mind is that of _being known_, in order to consider two lines of argument by which it may be defended. According to the first of these, the view of the plain man either is, or at least involves, materialism; and materialism is demonstrably absurd. The plain man's view involves the existence of the physical world prior to the existence of the knowledge of it, and therefore also prior to the existence of minds which know it, since it is impossible to separate the existence of a knowing mind from its actual knowledge. From this it follows that mere matter, having only the qualities considered by the physicist, must somehow have originated or produced knowing and knowing minds. But this production is plainly impossible. For matter, possessing solely, as it does, characteristics bound up with extension and motion, cannot possibly have originated activities of a wholly different kind, or beings capable of exercising them.