Consciousness is a quality of the mind generally regarded to comprise qualities such as subjectivity, self-awareness, sentience, sapience, and the ability to perceive the relationship between oneself and one's environment. Philosophers divide consciousness into phenomenal consciousness which is experience itself and access consciousness which is the processing of the things in experience (Block 2004).

In common parlance, consciousness denotes being awake and responsive to one's environment; this contrasts with being asleep or being in a coma. The term 'level of consciousness' denotes how consciousness seems to vary during anesthesia and during various states of mind such as day dreaming, lucid dreaming, imagining etc. Nonconsciousness exists when consciousness is not present. There is speculation, especially amongst religious groups, that consciousness may exist after death or before birth.

Consciousness is notoriously difficult to define or locate. Many cultures and religious traditions place the seat of consciousness in a soul separate from the body. Conversely, many scientists and philosophers consider consciousness to be intimately linked to the neural functioning of the brain.

An understanding of necessary preconditions for consciousness in the human brain may allow us to address important ethical questions. For instance, to what extent are non-human animals conscious? At what point in fetal development does consciousness begin? Can machines ever achieve conscious states? These issues are of great interest to those concerned with the ethical treatment of other beings, be they animals, fetuses, or in the future, machines.

Consciousness and language:
Because humans express their conscious states using language, it is tempting to equate language abilities and consciousness. There are, however, speechless humans (infants, feral children, aphasics), to whom consciousness is attributed despite language lost or not yet acquired. Moreover, the study of brain states of non-linguistic primates, in particular the macaques, has been used extensively by scientists and philosophers in their quest for the neural correlates of the contents of consciousness.

Cognitive neuroscience approaches:
Modern investigations into and discoveries about consciousness are based on psychological statistical studies and case studies of consciousness states and the deficits caused by lesions, stroke, injury, or surgery that disrupt the normal functioning of human senses and cognition. Read more...