Page:Popular Science Monthly Volume 12.djvu/65

 You could make out nothing, though you had as many eyes as the "devil's-darning-needle" of our boyhood, and each eye were "in fine frenzy rolling." Call, now, that cellar the universe, and then see if you can show cause why we may not consider the sense of sight as practically gone, and all knowledge that comes through sight a scaled book; ay, more, that nothing would be left to give us a hint that such knowledge could possibly exist.

How is it that we receive knowledge through the ear? By noting the difference between sounds, and between sound and silence. But, if there were no difference, there could be no hearing. If we had always listened only to a single tone, varying neither in pitch nor force, we should not be aware of the sense of hearing. We should be as one born deaf. It is the difference of sounds that gives us through the ear knowledge and harmony.

As with the senses named, so with smell, taste, and touch. Did all substances affect these senses in exactly the same way, however acute those senses, we should not be aware of their existence. Ask any one what is the smell of pure air, and he will tell you, "No smell." But how do we know that to be the case? As it has always been in contact with our smelling-nerves, we cannot judge of its odor. A dweller in Jupiter coming to visit his mundane cousins might, when he struck our atmosphere, expand his nostrils, as one sniffs the air when he all at once smells something very nice, or he might turn up his Jovian nose, as though he smelt something very bad. It is an open question whether or not the atmosphere is odorless, or, as a layman would put it, whether it smells the same as empty space. Could an intelligent man be put under an exhausted receiver, get the smell of a perfect vacuum, and survive to tell about it, he might throw some light on the question.

To sum up my reasoning, it comes to this: Were the universe one of sameness, instead of the universe of differences that it is, we should be unconscious of any external world, or of our own existence, no matter though we were the best-born specimens of the scientific stirpiculturist. In fact, we should be an army of negations. I am aware there is something a little queer in the logic of this paragraph, but yet there is a great deal of sound logic in it after putting aside the "queer," which will, however, pass current with all except professional detectives.

2. Relation to Knowledge.—What is knowledge? Only a perception of differences. How is a knowledge of natural history, for instance, obtained? Simply by finding out differences. In this way child and philosopher classify the horse and the ox. Progress in knowledge is possible in proportion—1. To objective differences; and, 2. To perceptive ability. Take botany. It is easy to classify those plants which have obvious differences into genera; but, when we come to the classification of sub-species, the work is more difficult. A