Merian studied at the University of Basle, gaining his doctorate in 1740. He became a member of the Class for Speculative Philosophy of the Berlin Academy in 1750, and director of the Class for Belles-Lettres in 1771. From 1797 he was permanent Secretary of the Academy.
Merian translated the work of David Hume into French. He published widely in the Mémoires of the Academy. A series of essays on the Molyneux problem appeared in the 1770s.