Condillac attempted a rigorous understanding of the relations between sensation and cognition. D’Alembert was a long-term (and fond) friend, Rousseau another. Rousseau, met as wayward tutor to Condillac’s brother’s children, introduced him to Diderot: both were regular dining companions (as was Buffon), and Diderot helped him find a publisher. Maupertuis, Beccaria, La Condamine and Voltaire were all correspondents. Montesquieu and Marivaux were met at the salon run by d’Alembert’s mother; despite his closeness to d’Alembert and Diderot, it’s thought Condamine wasn’t an Encyclopédiste.