THREE:After much searching, we have not been able to find the originals of the two passages quoted by Sir A. Grant. We have, however, found others setting forth the doctrine of Natural Realism with a clearness which leaves nothing to be desired. Aristotle tells us that former naturalists were wrong when they said that there could be no black or white without vision, and no taste without tasting; that is, they were right about the actuality, and wrong about the possibility; for, as he explains, our sensations are produced by the action of external bodies on the appropriate organs, the activity being the same while the existence is different. A sonorous body produces a sound in our hearing; the sound perceived and the action of the body are identical, but not their existence; for, he adds, the hearer need not be always listening, nor the sonorous body sounding; and so with all the other senses.267By examining the subject of applied mechanics and shop manipulation, a learner may see that the knowledge to be acquired by apprentices can be divided into two departments, that may be called general and special. General knowledge relating to tools, processes and operations, so far as their construction and action may be understood from general principles, and without special or experimental instruction. Special knowledge is that which [7] is based upon experiment, and can only be acquired by special, as distinguished from general sources.
