The philosophical position that only one's own mind is certain to exist, and that the external world and other minds cannot be known or may not exist.

From the Latin solus (alone) and ipse (self), meaning literally the self alone — the idea that the self is the only knowable or verifiable reality.

Considered by many philosophers to be an irrefutable but useless position — impossible to disprove yet equally impossible to act upon.

Russell and Moore's development of analytical philosophy was partly a reaction against the perceived slide toward solipsism in post-Kantian German idealism.

Descartes' famous cogito ergo sum was initially a solipsist argument — the 'I think, therefore I am' being a starting point from which he intended to prove only his own existence.