I didn’t read enough of Burtt’s book or even the chapter to judge the question, it’s possible he treats motivation as foundation, possible this part wasn’t a claim about a foundation. I do suspect he isn’t using the word “foundation” the way you are. At least, maybe Kepler regarded his theology as of the same type as you’re treating Einstein, i.e., foundation is a subjective belief? The things we’d know if we read the book. :P
I didn’t read enough of Burtt’s book or even the chapter to judge the question, it’s possible he treats motivation as foundation, possible this part wasn’t a claim about a foundation. I do suspect he isn’t using the word “foundation” the way you are. At least, maybe Kepler regarded his theology as of the same type as you’re treating Einstein, i.e., foundation is a subjective belief? The things we’d know if we read the book. :P