Many philosophers have admitted tropes into their scheme of things: Aristotle, Locke, Spinoza and Leibniz, for example. What is distinctive in Williams is not that tropes are admitted as a category, but as the only fundamental category, a trope-based form of what Schaffer calls “property primitivism.” (Schaffer 2003, 125). All else is constructed out of tropes, including concrete particulars and general properties, whereas tropes themselves are not constructed out of anything else, for example, out of a substance, a universal and the relation of exemplification. Not surprisingly, various aspects of Williams’ trope primitivism have been subjected to serious philosophical challenges either directly or indirectly.