solipsism

n. theory that the self is the only existing or knowable thing (Philosophy)

Solipsism (Latin: solus, alone + ipse, self) is the philosophical idea that "My mind is the only thing that I know exists". Solipsism is an epistemological or metaphysical position that knowledge of anything outside the mind is unjustified. The external world and other minds cannot be known and might not exist. In the history of philosophy, solipsism has served as a skeptical hypothesis.
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Noun
1. (philosophy) the philosophical theory that the self is all that you know to exist
(hypernym) philosophical doctrine, philosophical theory
(classification) philosophy

(n.)
Egotism.
  

(n.)
Egoism.
  

    The view that all we know is our own consciousness and we cannot be sure that anything exists outside of our own minds.  In other words, we might be just imagining that each other, the chairs we sit in, the tea we drink, is real.