All inquiry is conducted in the present of those investigators and is constrained by their present concerns. CBR is one important route perhaps the most important by which previous work is adapted to current problems. CBR begins from a current problem situation and seeks matches with past cases, rather than the other way around. Therefore, CBR, like all adaptation of inherited resources to current concerns, is whiggish. While CBR can be conservative, so can RBR, especially when rules are complete, whence very little learning can occur.
Revolutionary breakthroughs are often rule-breaking.
Or we speak of breaking out of the old conceptual framework. Such revolutions alter the system of rules. Of course, we could also speak of a systematic change in CBR as also breaking out of the old framework of concepts and practices. Insofar as science and engineering are CBR and not simply RBR, they are more rhetorical and less logical. Addendum on combinatorial chemistry.