Cognitive dissonance is a discomfort caused by holding conflicting cognitions (e.g., ideas, beliefs, values, emotional reactions) simultaneously. In a state of dissonance, people may feel surprise, dread, guilt, anger, or embarrassment. The theory of cognitive dissonance in social psychology proposes that people have a motivational drive to reduce dissonance by altering existing cognitions or adding new ones to create consistency. The diagram to the right shows a new cognition being integrated into a person's belief system to resolve such a conflict. An example of this would be the conflict between wanting to smoke and knowing that smoking is unhealthy; a person may try to change their feelings about the odds that they will actually suffer the consequences, or they might add the consonant element that the smoking is worth short term benefits.

In psychology and logic, rationalization (also known as making excuses) is an unconscious defense mechanism in which perceived controversial behaviors or feelings are logically justified and explained in a rational or logical manner in order to avoid any true explanation, and are made consciously tolerable-- or even admirable and superior-- by plausible means. Rationalization encourages irrational or unacceptable behavior, motives, or feelings and often involves ad hoc hypothesizing. This process ranges from fully conscious (e.g. to present an external defense against ridicule from others) to mostly subconscious (e.g. to create a block against internal feelings of guilt).