Kant's rather obscure and scattered references to the doctrine of transcendental or objective affinity in the first edition version of the Transcendental Deduction are generally regarded as directed against Hume, and specifically against the latter's sceptical reflections on the principle of the uniformity of experience, i.e. the claim that future associations of events will necessarily conform to past ones.¹The gist of Hume's contention is that this principle is neither demonstrable a priori (since its opposite is conceivable) nor a valid empirical inference (any such inference being obviously circular). But since these are the only two ways of acquiring knowledge, Hume concludes that we can have no rational insight into the necessity of this uniformity, and that our belief therein is due solely to custom or habit. As Kant himself was well aware, Hume's argument is not directed against the practical necessity or indispensability of this belief, but against its objective validity or foundation in reason. From Hume's sceptical standpoint this uniformity, and consequently the continued conformity of experience to our custom- induced expectations remains a brute and inexplicable fact in which we must believe, but can never understand.