The branch of philosophy that studies existence is metaphysics. Metaphysics
identifies the nature of the universe as a whole. It tells men what kind of
world they live in, and whether there is a supernatural dimension beyond it. It
tells men whether they live in a world of solid entities, natural laws,
absolute facts, or in a world of illusory fragments, unpredictable miracles,
and ceaseless flux. It tells men whether the things they perceive by their
senses and mind form a comprehensible reality, with which they can deal, or
some kind of unreal appearance, which leaves them staring and helpless.