[H]ow can that mean be called quite free at the same point of time and in regard to the same action in which and in regard to which he is nevertheless subject to an unavoidable nature necessity? It is a wretched subterfuge to seek to evade this by saying that the kind of determining grounds of his causality in accordance with natural law agrees with a comparative concept of freedom (according to which that is sometimes called a free effect, the determining natural ground of which lies within the acting being, e.g., that which a projectile accomplishes when it is in free motion )
Some people think that freedom and determinism are compatible. The most promising way of pursuing this idea is to compare interrupted behavior with behavior that is allowed to develop without interference. We can agree that shackles prevent a person from being free, regardless of the truth or falsity of determinism, because they prevent his intentions from being expressed in the world. So, the person who takes freedom and determinism to be compatible may hold that a person can be free if he can express his intention in action with no interference, even if his mental state is determined by the past and it, in turn, determines his actions. Kant claims that on their view, a projectile or a clock is free, for it, too, can sometimes act without interference. To Kant, this is absurd. The only alternative, if one believes in both determinism and freedom, is to take freedom as causation from the noumenal realm, where determinism does not apply.