Full Idea
As standardly construed, reduction can be either explanatory or ontological. Explanatory reduction is the strongest sort of reduction. ...Ontological reduction can still have an 'explanatory gap'.
Gist of Idea
Explanatory reduction is stronger than ontological reduction
Source
Robert Hanna (Rationality and Logic [2006], 1.1)
Book Reference
Hanna,Robert: 'Rationality and Logic' [MIT 2006], p.6