But besides this formal time condition, the objects of empirical cognition are determined, or, so far as we can judge a priori, are determinable, in various ways, so that specifically differentiated natures, over and above what they have in common as things of nature in general, are further capable of being causes in an infinite variety of ways; and each of these modes must, on the concept of a cause in general, have its rule, which is a law, and, consequently, imports necessity: