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 hypothet