Kant asserts that humans can influence events through their free wills. We can use “autonomous” and “free” interchangeably to describe the will because a rational will would have to be free to be self-legislating. As such, a will can only attain true freedom when it is pursuing morality. This establishes morality as a byproduct of freedom. Kant writes, “For since morality serves as a law for us only as for rational beings, it must hold for all rational beings as well, and as it must be derived solely from the property of freedom, freedom must also be proved as a property of the will of all rational beings [...]” (57, 4:448). He states a free will would have to follow the categorical imperative since it relies on maxims that encourage reason. Kant concedes that this might be difficult to conclusively prove but says we can use a priori cognition to realize we are in control of our own reason. He wants to use a positive conception of freedom in his discussion, meaning he will refer to freedom to act in a certain way.

Kant then asks why free-willed rational beings would agree to subject themselves to the categorical imperative.