According to Kant’s Universal Law Formula, maxims that cannot be conceived as universal laws denote duties of perfect obligation. In the recent literature, two versions of the Contradiction in Conception test have received the most attention. When acting on a maxim would violate a perfect duty, according to the Logical Contradiction Interpretation (LCI), universalizing the maxim would make it literally impossible to perform the action as described in the original maxim. According to the Practical Contradiction Interpretation (PCI), the locus of (...) the contradiction is as follows: the agent acts on the maxim in order to achieve some purpose, but were the agent’s maxim universalized, the purpose would be unattainable. Having examined the most widely accepted versions of both interpretations, I argue that i) PCI cannot generate contradictions for the maxims of any actions that violate perfect duties beyond those generated by LCI, ii) despite claims of its proponents, PCI cannot solve the vexing problem of relevant descriptions that Kant’s account faces, and iii) other arguments in favor of PCI are at best inconclusive. I therefore conclude that since LCI better coheres with the text, sympathetic interpreters should focus their efforts on LCI, not PCI. (shrink)