Core principle (5)
I believe the answer is:
basis
(Other definitions for basis that I've seen before include "First principle" , "Principle on which a theory is founded" , "Principal element" , "Reason" , "Underlying support for a theory" .)
I believe the answer is:
basis
(Other definitions for basis that I've seen before include "First principle" , "Principle on which a theory is founded" , "Principal element" , "Reason" , "Underlying support for a theory" .)