 In order to make a trial with Hume’s problematic concept (his crux metaphysicorum), namely the concept of cause, first, there is given to me a priori, by means of logic, the form of a conditional judgment in general, namely, to use a given cognition as ground and the other as consequent. It is possible, however, that a rule of relation is found in perception which says that a given appearance is constantly followed by another (but not conversely); and this is a case for me to employ the hypothetical judgment and, e.g., to say: if a body is illuminated sufficiently long by the sun, then it becomes warm. Here, there is certainly no necessity of connection as yet, and thus [not] the concept of cause. However, I continue and say that, if the above proposition, which is merely a subjective connection of perceptions, is to be a judgment of experience, then it must be viewed as necessary and universally valid. But such a proposition would be: the sun is through its light the cause of heat. The above empirical rule is now viewed as a law—and, in fact, not as valid merely of appearances, but [valid] of them on behalf of a possible experience, which requires completely and thus necessarily valid rules.