Abstract: The primary purpose of this paper is to establish that some aspects of Locke?s philosophy can be read as an anticipation of Kant?s idealism. The paper consists of three main parts. In the first part, I examine the continuity of the conception of substance that exists between otherwise very different philosophical systems of Aristotle and Descartes. Identifying the difference between the questions of ?what? substance is and that to which the concept refers, I examine in some detail Locke?s conception of substance, as well as his distinction between nominal and real essence, the latter being unknowable just like the substance. This unknowable character leads Locke to claim that we can cognize only one side of the existing world - the nominal one. In that sense, there is a striking parallel between the aforementioned distinction and the one Kant draws between appearance and the thing-in-itself. I also introduce philosophy of Richard Burthogge and his corresponding distinction I attempt to show how Locke indeed was anticipating Kant?s idealism, even if he wasn?t an idealist himself. Aside from anticipating the content of some of Kant?s basic tenets, I also attempt to show how Locke is also anticipating the Kant?s way of arguing for one of the essential components of his idealism - the thing-in-itself, where I draw the parallel between that concept and the concept of real essence.