But physicists like other "hard science" investigators - and mathematicians - are careful to lay out their axioms or presuppositions. Einstein's Relativity takes a four dimensional space/time continuum as an axiom. Likewise, high energy particle physicists presuppose the quantum mechanical level rather than the classical or astronomical level. But Darwin, as betty boop describes, did not define his subject, what life "is."
Darwin took the existence of life as axiomatic. Newton did not define what mass, space, and time were, and where they came from.