Abstract
The concept of necessity plays a central role in Kant's philosophy, but seems to lead to severe paradoxes. On the one hand he states: ‘Notwendigkeit und strenge Allgemeinheit sind sichere Kennzeichen einer Erkenntnis a priori’. On the other hand he talks also about ‘notwendig (d. i. nach einer Regel)’, which means ‘necessary according to the empirical natural laws’. However, he never states explicitly the distinction between these two different concepts of necessity. Either Kant's philosophy is inconsistent or we have to assume that he indeed interchanges two different concepts, even if he does not tell us that there is a difference between synthetic apriori necessity and natural necessity. This paper defends the hypothesis of two different necessities and then shows how this strategy makes possible a rational reconstruction of Kant's epistemology.