met·a·phys·ics

– noun
1. the branch of philosophy that treats of first principles, includes ontology and cosmology, and is intimately connected with epistemology.
2. philosophy, esp. in its more abstruse branches.
3. the underlying theoretical principles of a subject or field of inquiry.

on·tol·o·gy

– noun
1. the branch of metaphysics that studies the nature of existence or being as such.

cos·mol·o·gy

– noun
1. the branch of philosophy dealing with the origin and general structure of the universe, with its parts, elements, and laws, and esp. with such of its characteristics as space, time, causality, and freedom.
2. the branch of astronomy that deals with the general structure and evolution of the universe.

e·pis·te·mol·o·gy

– noun
1. a branch of philosophy that investigates the origin, nature, methods, and limits of human knowledge.