There are therefore two realities, the reality of our felt experience from which all thinking sets out, and the reality which in thinking we seek to know. The one reality is immediate; it is conscious experience itself. The other reality is that which we infer from the fact of experience, that by which we seek to explain our existence. The one we feel, the other we think. If the difference between immediate knowledge and mediate knowledge or inference lay in the feeling of certainty alone or in the nature of belief, the distinction would not be the difficult one that it is. The theories of idealism and realism show how widely philosophers are divided on the subject. We are quite as certain of some of the things that we can only infer as we are of the things of which we are immediately aware. We cannot doubt, for instance, that there are other persons besides ourselves, yet we can have no distinct knowledge of any consciousness but one--our own. Our knowledge that there are other minds is an inference from our observation of the behaviour of some of the things we {17} directly experience, and from the experience of our own consciousness. And even those things which seem in direct relation to us--the things we see, or hear, or touch--are immediately present in only a very small, perhaps an infinitesimal, part of what we know and think of as their full reality; all but this small part is inferred. From a momentary sensation of sight, or sound, or touch we infer reality that far exceeds anything actually given to us by the sensation. Thinking is questioning experience. When our attention is suddenly attracted by something--a flash of light, or a sound, or a twinge of pain--consciously or unconsciously we say to ourself, What is that? The _that_--a simple felt experience--contains a meaning, brings a message, and we ask _what_? We distinguish the existence as an appearance, and we seek to know the reality. The quest of the reality which is made known to us by the appearance is the logical process of thought. The end or purpose of this logical process is to replace the immediate reality of the felt experience with a mediated-reality--that is, a reality made known to us. Directly, therefore, that we begin to think, the immediately present existence becomes an appearance, and throughout the development of our thought it is taken to be something that requires explanation. We seek to discover the reality which will explain it.