Are you in a universe which is ruled by natural laws and, therefore, is stable, firm, absolute — and knowable? Or are you in an incomprehensible chaos, a realm of inexplicable miracles, an unpredictable, unknowable flux, which your mind is impotent to grasp? Are the things you see around you real — or are they only an illusion? Do they exist independent of any observer — or are they created by the observer? Are they the object or the subject of man’s consciousness? Are they what they are — or can they be changed by a mere act of your consciousness, such as a wish?
The nature of your actions — and of your ambition — will be different, according to which set of answers you come to accept. These answers are the province of metaphysics — the study of existence as such or, in Aristotle’s words, of “being qua being” — the basic branch of philosophy.
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.