received in rapid succession two sensations, first, that of a violent approximation to the inkstand, secondly, a sudden shock of pain. Having received this pair of sensations very frequently, he cannot help associating them together in his thoughts; so that now the thought of a violent approximation to the inkstand necessarily suggests to him the thought that it is not-to-be-approached-violently, or "hard." He began by learning to expect that perhaps, or probably, the first sensation would be followed by the second; but having found, after constant experiments, that the second sensation, so far as his experience goes, always follows the first, he gradually passes from belief into certainty, or knowledge, that the second always will, or must, follow the first.
A similar transition is going on at the same time in the infant's mind—I mean the transition from belief to certainty—in regard to thousands of other propositions besides the one we have selected, "this inkstand is hard." Every single case of such transition facilitates the transition in other cases, by making the child feel that, if he is to get on in the world and make his way through it without incurring the constant pains and penalties of Nature, he must not disregard these juxtapositions, or pairs of sensations, (which, when he grows older, he will, if ever he becomes an educated man, call "cause" and "effect"), but must take them to heart and remember them; when the first of a familiar pair comes, he must be prepared to find the second immediately following. Not unfrequently the child's limited experience associates together in his mind sensations that Nature has not associated; as, for example, when he infers that a clock must tick because he has never yet in his life seen a clock that has stopped. In this and other cases the child has afterwards to dissociate what he had too hastily joined together, and to correct his conclusions by wider experience. But, on the
