This book is in one sense a critique of metaphysics usually viewed as an attempt to explain the existence of the world in terms of a reality which is regarded as the ultimate cause or source of the world, and in another sense to understand metaphysics as a profoundly significant attempt to know or understand the true or real nature of what is there, or what we all experience empirically, or the world. Most of the philosophers belonging to different schools of philosophy tried to understand the world in terms of a reality which is supposed to be the explanation of it. However, in the other approach to metaphysics which we discern in the philosophy of Shankara, and which is in tune with the basic insights of the Upanishads, a comprehensive attempt is made to know or understand the true or real nature of what we know empirically, or the world before any attempt is made to explain its existence. We therefore tried to analyse and understand critically the basic concepts involved in the ontological problem of Brahman, like the nature of the world, its causal explanation, nature and ontological status of matter, consciousness and its relation to spirit or self with a view to understanding the Advaitic insight that Brahman is the true nature of what we experience and know empirically, or the world.