According to Kant, the arguments of rational psychology are formal fallacies that he calls transcendental paralogisms. It remains heavily debated whether there actually is any formal error in the inferences Kant presents: according to Grier and Allison, they are deductively invalid syllogisms, whereas Bennett, Ameriks, and Van Cleve deny that they are formal fallacies. I advance an interpretation that reconciles these extremes: transcendental paralogisms are sound in general logic but constitute formal fallacies in transcendental logic. By formalising the paralogistic inference, I will pinpoint the error as an illegitimate existential presupposition. Since - unlike transcendental logic - general logic abstracts from all objects, this error can only be detected in transcendental logic.