Full Idea
The only sure way of distinguishing lawful and accidental universal statements is to point out that in the former cases we see why the regularity must hold, while in the latter case we do not.
Gist of Idea
In lawful universal statements (unlike accidental ones) we see why the regularity holds
Source
Harré,R./Madden,E.H. (Causal Powers [1975], 2.II)
Book Reference
Harré,R/Madden,E.H.: 'Causal Powers: A Theory of Natural Necessity' [Blackwell 1975], p.37
A Reaction
I agree with this, and also take it to be the solution to the problem of induction. That smoking causes cancer will be a true generalisation but not a law, until we see clearly why it happens.
Related Idea
Idea 16942 It is hard to see how regularities could be explained [Quine]