Full Idea
In justification logics, the logics of knowledge are extended by making reasons explicit. A logic of proof terms was created, with a semantics. In this, mathematical truths are known for explicit reasons, and these provide a measure of complexity.
Gist of Idea
Justication logics make explicit the reasons for mathematical truth in proofs
Source
Melvin Fitting (Intensional Logic [2007], 3.6.1)
Book Reference
'Stanford Online Encyclopaedia of Philosophy', ed/tr. Stanford University [plato.stanford.edu], p.23