portal: Mind and Brain

Consciousness is a word often used in everyday speech to describe being awake and aware – responsive to the environment, in contrast to being asleep or in a coma. In philosophical and scientific discussion however, the term is restricted to a more precise meaning related to the specific way in which humans are mentally aware in such a way that they distinguish clearly between themselves (the thing being aware) and all other things and events.

This "self-awareness" may involve thoughts, sensations, perceptions, moods, emotions, and dreams.

Consciousness is the subject of much research in philosophy of mind, psychology, neuroscience, cognitive science, and artificial intelligence. Issues of practical concern include how the presence of consciousness can be assessed in severely ill or comatose people; whether non-human consciousness exists and if so how it can be measured; at what point in fetal development consciousness begins; and whether computers can achieve conscious states. Stuart Shieber (ed): The Turing test : verbal behavior as the hallmark of intelligence, Cambridge, Mass, MIT Press, 2004, ISBN 978-0-262-69293-9 Steven Marcus: Neuroethics: mapping the field. Dana Press, New York 2002. ISBN 978-0-9723830-0-4.

Etymology

The word "conscious" is derived from Latin conscius meaning "1. having joint or common knowledge with another, privy to, cognizant of; 2. conscious to oneself; esp., conscious of guilt".

A related word was conscientia which primarily means moral conscience. In the literal sense, "conscientia" means knowledge-with, that is, shared knowledge. The word first appears in Latin juridic texts by writers such as Cicero. Here, conscientia is the knowledge that a witness has of the deed of someone else.

In Christian theology, conscience stands for the moral conscience in which our actions and intentions are registered and which is only fully known to God. Medieval writers such as Thomas Aquinas describe the conscientia as the act by which we apply practical and moral knowledge to our own actions.

René Descartes (1596-1650) has been said to be the first philosopher to use "conscientia" in a way that does not seem to fit this traditional meaning, although this has recently been countered by Boris Hennig. In any event, John Locke had much influence on the 18th Century view of consciousness: in Samuel Johnson's celebrated Dictionary (1755), Johnson gives a definition of "conscious" as "endowed with the power of knowing one's own thoughts and actions," and takes Locke's own definition of "consciousness" as "the perception of what passes in a man's own mind."

Locke offered a definition of consciousness in his Essay Concerning Human Understanding (1690) that remained closely intertwined with moral conscience (I may be held morally responsible only for the act of which I am conscious of having achieved; and my personal identity - my self - goes as far as my consciousness extends itself).