 So far we have inquired only into the synchronic content of the Humean proposal. What sort principles of qualitative belief update does it underwrite? Leitgeb demonstrates an intimate relationship between the AGM revision principles and the Humean thesis: every agent that satisfies the AGM principles, as well as a weak version of the Lockean thesis, must also satisfy the Humean thesis. So if you think that AGM theory is the correct theory of rational qualitative belief update (and you believe that a high degree of partial belief is a  necessary condition of full belief) you must also accept the Humean thesis. More precisely, Leitgeb proves the following: