Solipsism

Solipsism (Latin: solus, alone + ipse, self) is an extreme form of skepticism, saying that nothing exists beyond oneself and one’s immediate experiences. More generally, it is the epistemological belief that one’s self is the only thing that can be known with certainty and verified (sometimes called egoism). Solipsism is also commonly understood to encompass the metaphysical belief that only one’s self exists, and that “existence” just means being a part of one’s own mental states, i.e. all objects, people, etc, that one experiences are merely parts of one’s own mind.