Full Idea
We must distinguish between entailment and validity as logical relations on the one hand, and inferring as a voluntary human activity on the other.
Clarification
The first two are part of pure logic, but 'inference' (from one idea to the next) is part of our natural rational thinking
Gist of Idea
Entailment and validity are relations, but inference is a human activity
Source
John Searle (Rationality in Action [2001], Ch.1.II)
Book Reference
Searle,John R.: 'Rationality in Action' [MIT 2001], p.21