Kant- The third antinomy of pure reason

As for the second two antinomies, Kant says that the dialectically opposed propositions of each contradict one another only if one takes appearances (phenomena) to be things in themselves(noumena). The thesis of the third antinomy is as follows: "There are in the world causes through freedom". The anthithesis: "There is no freedom, but all is nature". This is the same question that Hume took up when he considered liberty and necessity, except that Hume solved the problem by defining free will in a way that is compatible with determinism. Kant doesn't take that approach. Kant approaches the problem by asserting that one can actually be the first cause of a causal series, even if natural causal necessity exists. He does this by saying that the natural necessity of causality is part of the world of appearances, that is, the world of space, time, change, and natural law. While the phenomenal world requires there to be a cause for each event, the noumenal world can have what Kant calls 'spontaneity'. Spontaneous causes are uncaused causes. How is this possible? It is possible only through a will that acts according to rationality. Because the prescriptions of rationality are independent from time and change, acting according to rationality is acting according to something independent of the phenomenal world. The phenomenal world would still retain the appearance of a prior cause, while in the world of things in themselves an action can be spontaneous.