Solipsism is the theory that only the self exists, or can be proved to exist. The theory is unprovable like all good philosophical theories, and like all good philosophical theories it is also irrefutable.

It has in its favour the virtue of containing only those things that the solipsist knows about. This is because everything is part of the self and things which are unknown are not part of the self.

It has the disadvantage of containing all known things, such as space and time and trivial little things like galaxies and blackholes and so on.

The self as it comtemplates itself (what else is there?) sees other apparently independent entities much like itself. These 'other entities' can't really be independent entities, the self reasons, so they must be created by the self, (presumably to keep the self from becoming bored).

There are many problems with solipsism, the most obvious being the question of where the self is existing. It is hard to contemplate something existing without existing somewhere and that somewhere is, on the face of it, external to the self. Since solipsism contends that the self is all, how can there be anything external to the self.

One of the more interesting refutations of the above difficulty is to deny that existence needs a somewhere to exist in and that the apparent requirement for a somewhere is an illusion. One can consider something, the essence of a deity, existing, but not existing anywhere in this universe, this somewhere, without requiring a somewhere else.