There remains the consideration of Contrast, as a link of association. It is easy to show that both Contiguity and Similarity may enter into the association of contrasts. All contrasts that we are interested in are habitually coupled in language, as light and dark, heat and cold, up and down, life and death. Again contrasts suppose a common genus, that is a generic similarity; at least until we ascend to the highest contrast of all, the subject mind, and the object or extended world. Cold and Hot are grades of the common attribute called Temperature. As these links of contiguity and similarity are present, and of considerable strength, they practically lead to the mutual suggestion of contrasting things. Still, we cannot overlook the deeper circumstance that in contrast there is _relation_, and therefore mutual implication, so that the two members must always be virtually present, although they are not equally attended to. Heat has no meaning, no existence, but as a change from cold; the north implicates the south. We have two modes of regarding these relationships, which are distinguished by language, as if we {125} could abstract the one side from the other; that is, we think of heat apart from cold, and of the north apart from the south. But if one side is present, both must be present, and nothing is wanted but a motive, to make us reverse the conception, and bring into prominence the side that was in abeyance, cold instead of heat, south instead of north. This view of Contrast is variously expressed by Hamilton. (Reid, Note D * * *). Contrast, therefore, as an associating link, would draw from three sources, Relativity, Contiguity, and Similarity. It would also be heightened, in many instances, by the presence of strong feelings or emotions, as in the contemplation of startling changes, and the vicissitudes of things. Being one of the effects habitually introduced in Art and in Oratory, we are more than ordinarily impressed by the things so made use of--infancy beside old age, squalor following on splendour, abasement succeeding to elevation.