What is the refutation of idealism presented by Kant in his Critique of Pure Reason?

The idealism (material) is the theory that declares the existence of objects in space outside of ourselves is either merely doubtful and unprovable or false and impossible.
The first type of idealism is the problematic one of Descartes, who declared only one empirical assertion to be indubitable: 'I am.'
The second type of idealism is the dogmatic one of Berkeley, who declares that space, with all the things to which it is attached, as an indispensable condition, is something impossible in itself and therefore that things in space are mere imaginations.
The dogmatic idealism is inevitable when space is considered as a property that must belong to things in themselves, because then the existence of objects in space becomes impossible.