The importance of clearly perceiving that animals have a generic, as distinguished from an abstract, idea of causation—and, indeed, _must_ have such an idea if they are in any way at all to adjust their actions to their circumstances—the importance of clearly perceiving this is, that it carries with it a proof of the logic of recepts being able to reach generic ideas of _principles_, as well as of objects, qualities, and actions. In order to prove this important fact still more unquestionably, I will here quote a passage from the biography of the cebus which I kept for the express purpose of observing his intelligence. “To-day he obtained possession of a hearth-brush, one of the kind which has the handle screwed into the brush. He soon found the way to unscrew the handle, and, having done that, he immediately began to try to find out the way to screw it in again. This he in time accomplished. At first he put the wrong end of the handle into the hole, but turned it round and round the right way for screwing. Finding it did not hold, he turned the other end of the handle, carefully stuck it into the hole, and began again to turn it the right way. It was, of course, a very difficult feat for him to perform, for he required both his hands to hold the handle in the proper position, and to turn it between his hands in order to screw it in; and the long bristles of the brush prevented it from remaining steady, or with the right side up. He held the brush with his hind hands, but even so it was very difficult for him to get the first turn of the screw to fit into the thread; he worked at it, however, with the most unwearying perseverance until he got the first turn of the screw to catch, and he then quickly turned it round and round until it was screwed up to the end. The most remarkable thing was that, however often he was disappointed in the beginning, he never was induced to try turning the handle the wrong way; he always screwed it from right to left. As soon as he had accomplished his wish, he unscrewed it again, and then screwed it on again the second time rather more easily than the first, and so on many times.”