Full Idea
Kant maintained that metaphysics must be a body of necessary truths, and that necessary truths must be a priori, so metaphysical claims could not be justified by experience.
Gist of Idea
For Kant metaphysics must be necessary, so a priori, so can't be justified by experience
Source
report of Immanuel Kant (Critique of Pure Reason [1781]) by Tim Maudlin - The Metaphysics within Physics 3
Book Reference
Maudlin,Tim: 'The Metaphysics within Physics' [OUP 2007], p.78
A Reaction
I'm coming to the view that there is no a priori necessity, and that all necessities are entailments from the nature of reality. The apparent a priori necessities are just at a very high level of abstraction.
Related Idea
Idea 16257 Kant survives in seeing metaphysics as analysing our conceptual system, which is a priori [Maudlin]