 The distinction between perception and thought signaled Kant’s break with rationalist metaphysics but enabled him to deploy a divide-and-conquer strategy against dogmatic claims. By showing how each mode of apprehension involved certain necessary and distinct limitations on its employment, Kant was able to show that certain kinds of assertion in theology and metaphysics could not be genuine knowledge-claims. Perception was limited by the kinds of bodies we had and the manner in which we could be affected by external objects. We could not acquire scientific knowledge of the origins of the universe, or of our condition after death. Pure reason could not fill in details that were beyond all possible experience. The claims of metaphysics had to be synthetic, informative and not true by definition, yet a priori true. Arithmetic and geometry supplied synthetic a priori truths in abundance, and natural science supplied synthetic a posteriori truths, as well as exhibiting synthetic a priori propositions, such as the conservation of force.