Saint-Simon

there were two Fench writers of this name; Louis de Rouvroy, duc de Saint- Simon (1675-1755) was a chronicler (in 20 volumes) of the court of Louis XIV; Claude-Henri de Rouvroy comte de Saint-Simon (1760-1825) was a social philospher and political economist. Given the conjunction with Montaigne, James is more likely referring to the earlier of these.