In this refreshing and exceptional work, Rae Langton offers a new interpretation and defense of Kant's doctrine of "things in themselves." Kant distinguishes things in themselves from phenomena, thus making a metaphysical distinction between intrinsic and relational properties of substances. Langton argues that his claim that we have no knowledge of things in themselves is not idealism, but epistemic humility; we have no knowledge of the intrinsic properties of substances. This interpretation vindicates Kant's scientific realism and shows his primary/secondary quality distinction to be superior even to modern day competitors. And it answers the famous charge that Kant's tale of things in themselves is one that makes itself untellable.