Now, one pair of correlative categories that ap pears quite early in the development of thought is that of reality and illusion. A careful study of these will enable us to understand the skep tie's position. A changing object does not de ceive provided we know enough about the order of the changes. The trouble comes when an unexpected change occurs which throws us off our calculation. For example, we are accustomed to see broken sticks, and by some sort of opera tion we may be able to put the two broken ends together and practically make a whole stick again. But this requires time and work. We are not accustomed to seeing broken sticks straighten themselves of their own accord when they are moved. But now suppose we conic upon a stick projecting out of a clear pool of water. It looks broken; i.e. there is a break in the outline of the object as seen. Suppose now we lift it out of the water. It becomes straight in the operation. We didn't expect this change, and we are fooled. We find, however. that by passing our hand along the stick it feels straight; that is, the character and order of our tactual sensations in this case are what Bun- usually are when objects look straight. We dip the stick hack into the water. It looks broken again. Still keeping it under water, we pass our hands down the length of it and find that it feels straight although it looks crooked. We now lean on it. It bears our weight just as we have learned that straight-looking sticks do. Is the stick broken or not? We naturally an swer: It seems to be broken, but really it is not. The broken appearance is an illusion.
Now, what is the meaning of this answer? The most obvious meaning is, doubtless, the true one, as is suggested by the etymology of the word 'illusion.' Fhe broken appearance fools us; if we proceed on the supposition that it is broken we are disappointed. If. however, we proceed on the opposite supposition, we find that the event conforms to our expectation. The real qualities of the stick are those which do not de ceive us when we want to use it. The stick is really straight, because we can use it as we use straight sticks; we cannot use it as we do broken ones. Hence its brokenness is an illu sion. In other words, the distinction between reality and appearance is at tir,t a practical distinction. At this stage the two correlative categories are reality and illusion; if 'appearance' Is used it means 'illusion.' rhe important thing is that not every experience is an up pea ra nee. Only those experiences that fool us are not real. But after a while another stage of development is reached. It conies, for instance, to be noticed that a thin disk presents a circular outline when in one position, an oval outline when in another; it even has a rectilinear outline at times. 'None of these different qualities of outline is apt to deceive a keen observer who has had considerable experience. Hence in the preceding stage they were not called illusions.. But now attention gets' directed to this peculiar variability of the qualities of objects. Which of these variations is the real quality? Obviously again the one which is the basis for our calculations in our dealings with the object. The disk therefore is circular, though it looks oval or rectilinear. These various appearances are not illusions, be cause they do not usually fool us, but they are not real in the sense that they are variations from the qualities which the usable object has.
Appearance in this connection might be defined as a quality not itself real in the sense of be longing to the usable object ; but also not neces sarily illusory. Our eyes do not always see the object as it is, lint still they do not deceive us. What we do see helps us to infer what we do not sec, or the real quality. This real quality, however, can he seen if we put ourselves in the proper condition. For instance. the disk does have a visible circular outline if we hold it at right angles to our line of vision. Otherwise its outline, which in vision is elliptical or otherwise, is interpreted in thought as eireular.
But it is quite natural that this distinction be tween reality and appearance should not long satisfy. A further distinction is suggested by some such argument as the following: If our sense of sight can present an object in some other form than that which it really has, 110W e:111 we tell when its presentations are real or merely ap parent.? If the oval shape of the disk is merely an apparent shape, why may not the circular and every other shape he apparent also? In short. can our senses give us any other knowledge ex cept that of appearances? it is clear that such a question involves a change in the meaning of reality, which has hitherto had a practical rather than a theoretical significance. This change ap pears to he forced on us. when we have our at tention called to the fact that all our senses may deceive us. So long as it is our sense of sight that presents objects not as they really are, we can find what they are by appealing to the other senses. Reality is still a sensible thing. But what if every sense stands on the same foot ing with sight ? ('an one any longer appeal from sense to sense when every sense may give us only appearance? Must not reality he something supersensible? And if thought may miscarry, as it often dues, must we not say that reality tran scends even thought? Then how can we know that we know anything. about it ? The discovery of the fallibility of eveiv sense and of thought is the beginning of philosophic sorrow. The doctrine of the relativity (q.v.) of our knowledge begins to prevail. Historically there have been two different consequences of this doetrin2. A thinker may either hold to the no tion of a reality opposed to appearance. or he may find it so shadowy and unwarrantable a con ception that he gives it up altogether. Let us consider the former case, where the thinker gets into difficulty by being unable to say what real ity really is. The difficulty is for him insoluble, because he fails to see that he is trying to make a distinction to which no actually known differ ence corresponds. He is employing the cate gories of appearance and reality beyond their proper limits. The relation between appearance and reality was first recognized as holding be tween actually experienced qualities. Gradually the apparent qualities encroached on the pre serves of the real, until at last all real qualities were entirely ousted from the region of experi ence. Or, to put the same thing in other terms, a distinction which was first made as a recogni tion of a certain practical difference is now em ployed when that practical difference is no longer the matter in point.