THE Enlightenment polymath Denis Diderot turns 300 this year, and his October birthday is shaping up to be special. President François Hollande has indicated that he plans to honor the philosopher and novelist with what may be France’s highest tribute: a symbolic reburial in the Panthéon. In the roughly two centuries since this massive neo-Classical church was converted into a secular mausoleum, fewer than 80 people have been admitted into its gravestone club. If inducted, Diderot will arguably be the first member to be celebrated as much for his attacks on reigning orthodoxies as for his literary stature.