Adrian Moore develops a helpful distinction between good and bad metaphysics. Employing this distinction, I argue, first, that some contemporary metaphysical theories might be ‘bad’, insofar as they employ, unreflectively, concepts akin to Kant’s Ideas of reason. Second, I investigate the difficulty Kant himself has with explaining our craving for bad metaphysics. Third, I raise some problems for Kant’s doctrine of ‘transcendental cognition’, which rests on the difficult assumption that Ideas have objective reality. I conclude that, while Kant has given us means to combat certain bad metaphysics, his own philosophy is not entirely free of it either.