Were René Descartes and Pierre de Fermat alive at the same time?
Yes. René Descartes and Pierre de Fermat were alive at the same time for 42 or 43 years, from 1607 to 1650.
René Descartes was 10 or 11 when Pierre de Fermat was born.
Pierre de Fermat was 42 or 43 when René Descartes died, aged 53.
René Descartes
French philosopher, mathematician, and scientist
Born 31 March 1596 · died 11 February 1650, aged 53