Full Idea
A train of events following one another ever so regularly, could never lead us to the notion of a cause, if we had not, from our constitution, a conviction of the necessity of a cause for every event.
Gist of Idea
Regular events don't imply a cause, without an innate conviction of universal causation
Source
Thomas Reid (Essays on Active Powers 1: Active power [1788], 5)
Book Reference
Reid,Thomas: 'Inquiry and Essays', ed/tr. Beanblossom /K.Lehrer [Hackett 1983], p.306
A Reaction
Presumably a theist like Reid must assume that the actions of God are freely chosen, rather than necessities. It's hard to see why this principle should be innate in us, and hard to see why it must thereby be true. A bit Kantian, this idea.