There has recently been a growing interest in the topic of vagueness and indeterminacy in contemporary metaphysics, with two views taking center stage. The semantic view holds that indeterminacy is due to vagueness in the extension of concepts, while the ontological view holds that indeterminacy is due to the vagueness of certain objects. There has, however, been little research on discussions of vagueness and indeterminacy in early-modern philosophy despite the relevance of vagueness and indeterminacy for issues such as real and nominal definitions, clear and distinct ideas, and the principle of complete determination. In this paper, I survey discussions of vagueness in Locke, Leibniz, and Kant and point to ways in which the problem of vagueness and indeterminacy touches on broader issues in their respective philosophies. Although Locke, Leibniz, and Kant all suggest that vagueness is a semantic phenomenon, Kant also appears to countenance an ontological view according to which objects as appearances may sometimes be indeterminate.