The four key attributes of a fundamental explanatory structure are: irreducibility, generality, commensurability, and fertility. Because reductionism ultimately fails as an explanation of all things, a mutually commensurable set of fundamental ideas is required, as opposed to a single fundamental Theory of Everything. However, the unity of science is insured by the commensurable interrelationships between these fundamental (and thus irreducible) explanatory structures.
Gregory Derry