The term used to describe the belief in something that a person knows isn't true is "cognitive dissonance." Cognitive dissonance is a psychological term that refers to the state of discomfort or tension that arises when a person holds two or more contradictory beliefs, ideas, or values, or when their beliefs are inconsistent with their actions or experiences.
When individuals experience cognitive dissonance, they may feel uneasy, conflicted, or anxious because they recognize the inconsistency between their beliefs and reality. In an attempt to reduce this discomfort, people may employ various strategies, such as rationalization, denial, or avoidance, to maintain their current beliefs or justify their actions.
Cognitive dissonance is a common psychological phenomenon and can play a significant role in shaping attitudes, behaviors, and decision-making processes. It often influences how people interpret information and can impact their openness to new ideas or changing their minds when presented with evidence that contradicts their beliefs.