Jean de Silhon (1600–1667)and René Descartes (1596–1650) tried to develop positive knowledge claims that would avoid Gassendi’s skepticism. Silhon argued that knowledge was possible because it existed in logic and the sciences. Descartes based his entire philosophy on an attempt to demonstrate the existence of certain scientific knowledge that would not conflict with Church doctrine. In the end, the Jesuits upheld Gassendi’s view that certainty is impossible and condemned Descartes.