 For I take my reasonings to be so closely interconnected that just as the last are proved by the first, which are their causes, so the first are proved by the last, which are their effects. It must not be supposed that I am here committing the fallacy that the logicians call “arguing in a circle”. For as experience makes most of these effects quite certain, the causes from which I deduce them serve not so much to prove them as to explain them; indeed, quite to the contrary, it is the causes which are proved by the effects. And I have called them “suppositions” simply to make it known that I think I can deduce them from the primary truths I have expounded above. (Discourse VI, AT 6: 76, CSM 1: 150)