We see at once that we cannot stop here. We have really got a contradiction. If the parts of our world are connected with each other, they are not merely dependent upon us, that is, upon the changes of our consciousness. And we all take them to be independent of us, in the sense that we do not suppose the presence or absence of our perception to make any difference to the world except by the continuance or cessation of our perception of it or of its parts. This is the state of mind in which we practically live, philosophers and all. I do not really take notice of any difference in mode of existence between the wall in front of me, which I see, and the wall behind me, which I {8} do not see. While you are in this lecture-hall, if you think of your rooms at home, you think of them as they look, that is, as they would look if you were there to see them. How else, indeed, could you think of them? This is practically necessary, and therefore, for practical purposes, true. But if you take it as a theory, omitting the hypothetical factor, “if I was there to see,” you go wrong. You then treat your world as being, outside your consciousness, the same that it is inside your consciousness, without allowing for the withdrawal of your consciousness. You are then on the way to think that the world, _as you see, hear, and feel it_, is outside your mind, and that the sight, hearing, feeling, and the ideas born of them, are inside your mind as a sort of faint and imperfect _copy_ of the world which you then call “external,” _in the sense of outside the mind_. _Common sense_ i. The first position was that of common sense. The second is that of common-sense theory. Common sense is quite justified. It says, “Things affect each other, but the mere presence and absence of our perception does not affect them.” For practical purposes we must treat them as being, when unapprehended by our minds, just the same as when apprehended by our minds. This is the first idea or rather postulate--for it is not a theoretical idea--of objectivity. Objective = “independent of our consciousness for practical purposes.” _Common-sense theory_