The more "conciliance" a theory has, according to the biologist EO Wilson, the more explanatory power it holds at multiple levels of analysis. For example, the theory of gravity has (near perfect?) utility at both the macroscopic level of swirling galaxies as well as at the microscopic level of, say, the mitochondria swimming in our cells!
Even the best theory, however, can fail at the extremes, as does Newtonian physics when it reaches both Big Bang and Quantum states. Of course it does not follow from this that truth is merely relative (a falsehood root of post-modernism). However, there is the profound implication that any grand theory likely has constraints, and, perhaps more to the point, these limitations to knowledge are not always obvious...or even knowable.