Philosophical Studies. G. E. Moore

which seem to be necessary, though not sufficient, where observation is to give any reason for a generalisation, I may now proceed to my second preliminary question. What kinds of things do we observe?

      In order to illustrate how much and how little I mean by "observation" or "direct perception," I will take as an instance a very common visual perception. Most of us are familiar with the experience which we should describe by saying that we had seen a red book and a blue book side by side upon a shelf. What exactly can we be said to observe or directly perceive when we have such an experience? We certainly observe one colour, which we call blue, and a different colour, which we call red; each of these we observe as having a particular size and shape; and we observe also these two coloured patches as having to one another the spatial relation which we express by saying they are side by side. All this we certainly see or directly perceive now, whatever may have been the process by which we have come to perceive so much. But when we say, as in ordinary talk we should, that the objects we perceive are books, we certainly mean to ascribe to them properties, which, in a sense which we all understand, are not actually seen by us, at the moment when we are merely looking at two books on a shelf two yards off. And all such properties I mean to exclude as not being then observed or directly perceived by us. When I speak of what we observe, when we see two books on a shelf, I mean to limit the expression to that which is actually seen. And, thus understood, the expression does include colours, and the size and shape of colours, and spatial relations in three dimensions between these patches of colour, but it includes nothing else.

      But I am also using observation in a sense in which we can be said actually to observe a movement. We commonly say that we can sometimes see a red billiard ball moving towards a white one on a green table. And, here again, I do not mean to include in what is directly perceived or observed, all that we mean by saying that the two objects perceived are billiard-balls. But I do mean to include what (we should say) we actually see. We actually see a more or less round red patch moving towards a more or less round white patch; we see the stretch of green between them diminishing in size. And this perception is not merely the same as a series of perceptions—first a perception of a red patch with a green stretch of one size between it and the white; then a perception of a red patch with a green stretch of a different size between it and the white; and so on. In order to perceive a movement we must have a different perception from any one of these or from the sum of them. We must actually see the green stretch diminishing in size.

      Now it is undoubtedly difficult, in some instances, to decide precisely what is perceived in this sense and what is not. But I hope I have said enough to show that I am using "perceive" and "observe" in a sense in which, on a given occasion, it is easy to decide that some things certainly are perceived, and other things, as certainly, are not perceived. I am using it in a sense in which we do perceive such a complex object as a white patch moving towards a red one on a green field; but I am not using it in any sense in which we could be said to "perceive" or "observe" that what we saw moving was a billiard-ball. And in the same way I think we can distinguish roughly between what, on any given occasion, we perceive, as we say, "by any one of the other senses," and what we do not perceive by it. We can say with certainty that, on any given occasion, there are certain kinds of "content" which we are actually hearing, and others which we are not actually hearing; though with regard to some again it is difficult to say whether we are actually hearing them or not. And similarly we can distinguish with certainty in some instances, between what we are on a given occasion, actually smelling or feeling, and what we are not actually smelling or feeling.

      But now, besides these kinds of "things," "objects," or "contents," which we perceive, as we say, "by the senses," there is also another kind which we can be said to observe. Not only can I observe a red and blue book side by side; I can also observe myself observing them. I can perceive a red patch moving towards a white, and I can also perceive my perception of this movement. And what I wish to make as plain as I can is that my perception of the movement of a coloured patch can at least be distinguished from that movement itself. I wish to make it plain that to observe a coloured patch moving is to observe one thing; and to observe myself observing a coloured patch moving is another. When I observe my own perception of a movement, I observe something more than when I merely observe the movement, and something very different from the movement. I may perceive a red and a blue book side by side on a shelf; and at another time I may perceive a red ball moving towards a white. The red and blue patch, of one shape, at rest side by side, are different from the red, of another shape, moving towards the white; and yet, when I say that both are "perceived," I mean by "perceived" one and the same thing. And since, thus, two different things may both be perceived, there must also be some difference between each of them and what is meant by saying that it is perceived. Indeed, in precisely the same way In which I may observe a spatial relation between a red patch and a blue (when I observe them "side by side") I do, when I observe my own perception of them, observe a spatial relation between it and them. I observe a distance between my perception and the red and blue books which I perceive, comparable in magnitude with the breadth or height of the blue book, just as these are comparable in magnitude with one another. And when I say I observe a distance between my perception of a red book and that red book itself, I do not mean that I observe a distance between my eyes, or any other part of what I call my body, and the red patch in question. I am talking not of my eyes, but of my actual perception. I observe my perception of a book to be near the book and further from the table, in exactly the same sense in which I observe the book to be near the shelf on which it stands, and further from the table. And just as, if the distance between a red patch and a white is to be perceived, the red patch must be different from the white, so, if I perceive a certain distance between my perception and the red patch, my perception must be different from the red patch which I perceive.