Full Idea
A Newtonian philosopher …confesses his ignorance of the true cause of magnetic motion, and thinks that his business, as a philosopher, is only to find from experiment the laws by which it is regulated in all cases.
Gist of Idea
Scientists don't know the cause of magnetism, and only discover its regulations
Source
Thomas Reid (Essays on Active Powers 1: Active power [1788], 6)
Book Reference
Reid,Thomas: 'Inquiry and Essays', ed/tr. Beanblossom /K.Lehrer [Hackett 1983], p.312
A Reaction
Since there is a 'true cause', that implies that the laws don't actively 'regulate' the magnetism, but only describe its regularity, which I think is the correct view of laws.