Dialecticians claim that unity or identity of opposites can exist in reality or in thought. If the opposites were completely balanced, the result would be stasis, but often it is implied that one of the pairs of opposites is larger, stronger or more powerful than the other, such that over time, one of the opposed conditions prevails over the other. Yet rather than 'stasis' the identity of opposites, there being unity within their duality, is taken to be the instance of their very manifestation, the unity between them being the essential principle of making any particular opposite in question extant as either opposing force. For example 'upward' cannot exist unless there is a 'downward', they are opposites but they co-substantiate one another, their unity is that either one exists because the opposite is necessary for the existence of the other, one manifests immediately with the other. Hot would not be hot without cold, due to there being no contrast by which to define it as 'hot' relative to any other condition, it would not and could not have identity whatsoever if not for its very opposite that makes the necessary prerequisite existence for the opposing condition to be. This is the oneness, unity, principle to the very existence of any opposite. Either one's identity is the contra-posing principle itself, necessitating the other. The criteria for what is opposite is therefore something "a priori".