Possibly the most challenging and pervasive source of problems in the whole of philosophy. Our own consciousness seems to be the most basic fact confronting us, yet it is almost impossible to say what consciousness is. Is mine like yours? Is ours like that of animals? Might machines come to have consciousness? Is it possible for there to be disembodied consciousness? Whatever complex biological and neural processes go on backstage, it is my consciousness that provides the theatre where my experiences and thoughts have their existence, where my desires are felt and where my intentions are formed. But then how am I to conceive the āIā, or self that is the spectator of this theatre? One of the difficulties in thinking about consciousness is that the problems seem not to be scientific ones; Leibniz remarked that if we could construct a machine that could think and feel, and blow it up to the size of a mill and thus be able to examine its working parts as thoroughly as we pleased, we would still not find consciousness (Monadology, para. 17), and drew the conclusion that consciousness resides in simple subjects, not complex ones. Even if we are convinced that consciousness somehow emerges from the complexity of brain functioning, we may still feel baffled about the way the emergence takes place, or why it takes place in just the way it does.
The nature of conscious experience has been the largest single obstacle to physicalism, behaviourism, and functionalism in the philosophy of mind: these are all views that according to their opponents, can only be believed by feigning permanent anaesthesia. But many philosophers are convinced that we can divide and conquer: we may make progress by breaking the subject up into different skills and recognizing that rather than a single self or observer we would do better to think of a relatively undirected whirl of cerebral activity, with no inner theatre, no inner lights, and above all no inner spectator.
Philosophy dictionary. Academic. 2011.