Full Idea
Hume's account of the causal relation makes determinism less rigid because there is no longer a logical necessity in the succession of events.
Gist of Idea
Hume makes determinism less rigid by removing the necessity from causation
Source
comment on David Hume (Enquiry Conc Human Understanding [1748], VIII.II.75) by Jennifer Trusted - Free Will and Responsibility Ch.4
Book Reference
Trusted,Jennifer: 'Free Will and Responsibility' [OUP 1984], p.34