Victor Gijsbers provides the best explication and discussion of the concept of a scientific paradigm that I've seen, heard, read--anywhere. Required listening (only 10 minutes long).

The first video is called,  "Thomas Kuhn, Normal Science."
https://www.youtube.com/watch?v=sOGZEZ96ynI&list=PLPeStI124dee1ByfcDzRvPxKDNb0GQjmo&index=5

Paradigm: all the theories, concepts, methods and measuring instruments that a scientific discipline takes for granted and that directs research in that discipline. 

Normal science revolves around a well-functioning paradigm--in which the scientists in that field are confident. When within the paradigm, there are many things that scientists don't want to be critical about. At this phase of science, it's a waste of time to be critical about the paradigm.

We can answer detailed questions about history or any other subject because we can take a large theoretical and methodological background for granted. So we don't have to be critical about these things and can focus our thoughts on the single question before us.