 Note that Hume is here supposing that, in our idea of the relation between cause and effect, the “tye or connexion … which binds them together” is necessary (“it is impossible that any other effect could result”). In the corresponding section of the Treatise, Book 1, part 3, section 2 (“Of probability; and of the idea of cause and effect”), Hume makes this completely explicit (T 1.3.2.11; SBN 77): 