Unconsciousness is the absence of consciousness. Unconsciousness normally only occurs during sleep, and even then dreaming may involve partial or full consciousness of dream events. Unconsciousness may also occur from a concussion, during an epileptic seizure, as a result of intoxication, or due to some other medical condition (such as a neurological dysfunction), and during general anaesthesia.

Unconsciousness is not the same thing as the unconscious mind, which is assumed to operate even whilst the individual is conscious.

Law and medicine

In jurisprudence, unconsciousness is a possible defense by excuse; via which, a defendant may argue that they should not be held criminally liable for actions which broke the law. Courts rarely consider "falling asleep" (especially while driving or during surgery) to be an acceptable defense; however incidents related to epileptic seizure, neurological dysfunctions and sleepwalking may be considered acceptable.

On the other hand, someone who is less conscious can not give informed consent to anything. This is relevant in the case of sexual behavior (not allowed with such a person), and also in the case of a patient, with regard to starting or stopping a treatment, and euthanasia.

See also

• lucid dreaming
• hypnosis
• Do Not Resuscitate
• Living will