My goal in this paper is to show that it is not the case that positive duties can be derived from Kant’s so-called universalizability tests. I begin by explaining in detail what I mean by this and distinguishing it from a few things that I am not doing in this paper. After that, I confront the idea of a maxim contradictory, a concept that is advanced by many com- mentators in the attempt to derive positive duties from the universalizability tests. (...) I ex- plain what a maxim contradictory is and how the concept is used to derive positive duties. Then I argue that the notion of a maxim contradictory presupposes an objectionable form of maxim realism. I move from there to the idea of a maxim contrary and the deliberative field. These two ideas are used in tandem by commentators who do not appeal to maxim contradictories. I explain how these concepts are used to derive positive duties and then I argue that there is a systematic error in the derivations that enables one to see that they cannot work. (shrink)