This study reflects upon the fundamental justification of the radicality of Kant’s affirmation according to which religion is “a matter of reason alone”. To this end, this paper bores in two directions: In a first direction, the premises as well as the context of the Critique of Practical Reason’s thesis, according to which the moral law leads to religion, are reconstructed. The question that needs to be clarified in this context concerns the semantic content of the concept of religion that is introduced here in Kant’s argumentation. That question’s resolution will help to show the sense in which religion is not merely a matter of reason alone. In a second direction, further inquiries are made regarding Religion within the Limits of Reason Alone on the ‘plural relation’ between two discourses that originate in different sources – reason and revelation. This shows the sense in which revealed religion enriches reason’s discourse. In that respect, the complexity of the Kantian arguments does not allow us to maintain outright the thesis that religion is a matter of reason alone.