Denial is probably one of the best known defence mechanisms, used often to describe situations in which people seem unable to face reality or admit an obvious truth (i.e. "He's in denial."). Denial is an outright refusal to admit or recognize that something has occurred or is currently occurring. Drug addicts or alcoholics often deny that they have a problem, while victims of traumatic events may deny that the event ever occurred.
Denial functions to protect the ego from things that the individual cannot cope with. While this may save us from anxiety or pain, denial also requires a substantial investment of energy. Because of this, other defences are also used to keep these unacceptable feelings from consciousness. In many cases, there might be overwhelming evidence that something is true, yet the person will continue to deny its existence or truth because it is too uncomfortable to face. Denial can involve a flat out rejection of the existence of a fact or reality. In other cases, it might involve admitting that something is true, but minimizing its importance. Sometimes people will accept reality and the seriousness of the fact, but they will deny their own responsibility and instead blame other people or other outside forces.