In On a Discovery, Kant depicts monads as simple beings that are thought in the idea as the ground of appearances. He argues that his account of monads is partially in line with both Leibniz's monadology and his own critical philosophy. However, in the Critique of Pure Reason, Kant appears to depart from the monadologies of his predecessors. In this article, I make sense of Kant's late subscription to a version of Leibniz's monadology by arguing that Kant considers monads to (...) be the objects represented through cosmological and psychological ideas posited by reason in its search for the unconditioned conditions of appearances. In particular, I point to what I take to be two instances of what Kant calls “objects in the idea” in the Critique of Pure Reason, namely (a) the substratum of matter qua ground of external appearances, and (b) the soul qua ground of internal appearances. Drawing on Kant's reply to Eberhard and the Transcendental Dialectic of the first Critique, I highlight the merely regulative—and yet fundamental—role that monads conceived as objects of reason play in Kant's critical philosophy. (shrink)