 Hume’s contributions to the critical phase of the causation debate are contained in Treatise 1.3.6 and Section 4 of the first Enquiry, appropriately titled “Sceptical doubts concerning the operations of the understanding”. The constructive phase in his Enquiry account is the following section, also appropriately titled “Sceptical solution of these doubts”, while the corresponding sections of the Treatise stretch from 1.3.7 through 1.3.10. 