 In 1748, An Enquiry concerning Human Understanding appeared, covering the central ideas of Book I of the Treatise and his discussion of liberty and necessity from Book II. He also included material he had excised from the Treatise. In 1751, he published An Enquiry concerning the Principles of Morals, a “recasting” of Book III of the Treatise, which he described as “incomparably the best” of all his work (MOL 10). More essays, the Political Discourses, appeared in 1752, and Hume’s correspondence reveals that a draft of the Dialogues concerning Natural Religion was also underway at this time.