 The challenge Kant issues is to explain why, under normal conditions, the ordering in question is universal and necessary. Part of the best explanation, he believes, is (a), that we must have a faculty for ordering the representations. Hume might agree with this conclusion, supposing a sufficiently thin conception of ‘faculty’. Yet he would deny (b), that this faculty does not consist solely of sensory items. Kant argues that the Humean proposal for a faculty that consists solely of sensory items, the faculty of association, cannot account for the truth of propositions such as (U-N), for the very paradigms of association, such as word association, and the association of topics in a conversation, do not exhibit the requisite universality and necessity. The alternative that can account for the truth of propositions such as (U-N) involves affirming (c), that the faculty in question must be one that employs the categories.