Full Idea
In model theory, which has dominated the last decades, one concentrates on logically valid sentences, and what follows logically from what, but one disregards questions concerning how we know these things.
Gist of Idea
Model theory looks at valid sentences and consequence, but not how we know these things
Source
Dag Prawitz (On the General Idea of Proof Theory [1974], §1)
Book Reference
'A Philosophical Companion to First-Order Logic', ed/tr. Hughes,R.I.G. [Hackett 1993], p.215