Full Idea
Reasoning itself depends upon a grasp of possibilities, because a valid argument is one in which it is not possible for the conclusion to be false if the premises are true.
Gist of Idea
It is impossible to reach a valid false conclusion from true premises, so reason itself depends on possibility
Source
E.J. Lowe (A Survey of Metaphysics [2002], p.11)
Book Reference
Lowe,E.J.: 'A Survey of Metaphysics' [OUP 2002], p.11
A Reaction
A very valuable corrective to my pessimistic view of philosophers' attempts to understand metaphysical necessity. But if we can only grasp natural necessity, then all reason is naturalistic.