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only degrees of light

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only degrees of light

The child who has as yet had no experience of distance grasps at the moon, and does not correct its first impression as to the real distance until a second percept contradicts the first. Every extension of the circle of my percepts compels me to correct my picture of the world. We see this in everyday life, as well as in the mental development of mankind. The picture which the ancients made for themselves of the relation of the earth to the sun and other heavenly bodies, had to be replaced by another when Copernicus found that it contradicted percepts which in those early days were unknown. A man who had been born blind said, when operated on by Dr. Franz, that the idea of the size of objects which he had formed before his operation by his sense of touch was a very different one. He had to correct his tactual percepts by his visual percepts.


How is it that we are compelled to make these continual corrections in our observations?

A single reflection supplies the answer to this question. When I stand at one end of an avenue, the trees at the other end, away from me, seem smaller and nearer together than those where I stand. But the scene which I perceive changes when I change the place from which I am looking. The exact form in which it presents itself to me is, therefore, dependent on a condition which inheres, not in the object, but in me, the percipient. It is [56]all the same to the avenue where I stand. But the picture of it which I receive depends essentially on my standpoint. In the same way, it makes no difference to the sun and the planetary system that human beings happen to perceive them from the earth; but the picture of the heavens which human beings have is determined by the fact that they inhabit the earth. This dependence of our percepts on our points of observation is the easiest kind of dependence to understand. The matter becomes more difficult when we realise further that our perceptual world is dependent on our bodily and mental organisation. The physicist teaches us that within the space in which we hear a sound there are vibrations of the air, and that there are vibrations also in the particles of the body which we regard as the cause of the sound. These vibrations are perceived as sounds only if we have normally constructed ears the scene of a violent and murderous attack..


Without them the whole world would be for us for ever silent. Again, the physiologist teaches us that there are men who perceive nothing of the wonderful display of colours which surrounds us. In their world there are and dark. Others are blind only to one colour, e.g., red. Their world lacks this colour tone, and hence it is actually a different one from that of the average man. I should like to call the dependence of my perceptual world on my point of observation “mathematical,” and its dependence on my organisation “qualitative.” The [57]former determines proportions of size and mutual distances of my percepts, the latter their quality. The fact that I see a red surface as red—this qualitative determination—depends on the structure of my eye.

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