I soon comprehend that, since I cannot think anything without a category, I must also first seek out the category in reason's idea of freedom, with which I am now dealing, and here this is the category of causality; and I comprehend that, even though one cannot base the rational concept of freedom, which is a transcendent concept, on any corresponding intuition, nonetheless a sensible intuition must first be given to the concept of understanding (that of causality) for the synthesis of which the rational concept of freedom demands the unconditioned and thereby objective reality is first secured to the concept Now, all the categories are divided into two classes: the mathematical which aim merely at the unity of synthesis in the presentation of objects, and the dynamical, which aim at the unity of synthesis in the presentation of the existence of objects.