The Importance of Synthetic Apriori Propositions to Kant's metaphysics

Statement

Kant's advocacy for his metaphysics in Critique of Pure Reason can be seen as relying on the possibility of synthetic apriori claims. If synthetic apriori propositions are possible, it supposes a certain metaphysical worldview, much of the Critique of Pure reason then relies on the possibility of synthetic apriori propositions to justify a worldview. One could reduce Kant's argument into a simple form: If Kant's metaphysics is true, then synthetic apriori propositions are possible.