Solipsism

Derived from the Latin words solus ('only') and ipse ('self'), the term is sometimes used as a synonym for 'selfishness' or 'egotism'.

In philosophy it is used more strictly to describe the thesis that only the self exists.

All philosophies that, like the Cartesian cogito ('I am thinking, therefore I am'), take as their starting-point the immediate experience of an individual consciousness tends to lapse into solipsism as they have difficulty in establishing the existence of other consciousnesses.

Both Husserl's pure phenomenology and the existentialism of the early Sartre have been criticized for their alleged solipsism.