Page:Popular Science Monthly Volume 68.djvu/226

 222 things. However, our knowledge of fowls always begins with the experience of certain sensations of sight with which sensations of hearing and of touch may be associated. The sensations of sight, to which we will limit ourselves for the present, are by no means completely identical. According to its distance from us, we see the fowl as large or small; with changes in its position and its movements its contour is very different. As, however, we observe that these differences pass continuously into one another without exceeding certain limits, we overlook them and confine ourselves to certain other peculiarities (legs, wings, eyes, beak, comb, etc.) which remain constant and do not change. The constant properties we gather together as a 'thing': the changing ones we call the states of this thing. Among the changing ones we distinguish those which are dependent upon ourselves (e. g., distance) from those upon which we ourselves have no immediate influence (e. g., position and movements). The former we call the subjectively variable part of our experience, whereas we term the latter the objective variability of the thing.

To ignore the subjectively and objectively variable portion of our experiences, while we retain their constant parts, and to combine the latter into a single unity, is one of the most important operations which we base on our experiences. We term this procedure abstraction, and its product, the constant unit, a concept. Obviously this procedure contains arbitrary as well as essential parts. Quite arbitrary, or rather accidental, is the fact that according to the state of our attention, our training, nay even our whole intellectual make-up, quite different parts of any given experience reach our consciousness. We may overlook constant components and notice changing ones. But all components become of necessity objective as soon as we have noticed them. After once seeing the fowl black, it is no longer in our power to see it red. It follows that in general our knowledge of corresponding characteristics is less extensive than it might be, inasmuch as we have never noticed all that correspond. Our concept is, therefore, poorer at any given moment in components than it might be. To search for these hitherto overlooked components of a concept and to prove them a constant part of the corresponding experience is one of the never-ceasing labors of science.

The other possibility, viz., that certain components which do not prove to be constant have been incorporated into a concept, also occurs and leads to another problem. These questionable components may, on the one hand, be eliminated from the concept if further experiences show that the remaining ones are contained in them; or, on the other hand, a new concept may be formed by including the constant components and eliminating the inconstant ones. Thus for a long time the white color was a part of the concept 'Swan.' When the black swans of