👉 Illusion, or illusionism, is a philosophical and psychological concept that describes a phenomenon where information or reality appears to be distorted or altered in some way. It refers to mental distortions that are not based on objective facts but instead result from a person's perceptions of the world. In this sense, "illusory" means that something that is perceived as real may not actually exist. Illusions can take many forms, including hallucinations, delusions, and false beliefs. They can be