solipsism

from WordNet (r) 3.0 (2006)

solipsism
    n 1: (philosophy) the philosophical theory that the self is all
         that you know to exist

from The Collaborative International Dictionary of English v.0.48

Solipsism \So*lip"sism\, n. [L. solus alone + ipse self.]
   1. (Ethics) Egotism. --Krauth-Fleming.
      [1913 Webster]

   2. (Metaph.) Egoism. --Krauth-Fleming.
      [1913 Webster]