Were Jean-Jacques Rousseau and Napoleon alive at the same time?
Yes. Jean-Jacques Rousseau and Napoleon were alive at the same time for 8 years, from 1769 to 1778.
Jean-Jacques Rousseau was 57 when Napoleon was born.
Napoleon was 8 when Jean-Jacques Rousseau died, aged 66.
Jean-Jacques Rousseau
Genevan philosopher, writer, and composer
Born 28 June 1712 · died 2 July 1778, aged 66
Napoleon
French military leader, French Emperor 1804–1814 and again in 1815
Born 15 August 1769 · died 5 May 1821, aged 51