Ludwig Wittgenstein

This remark provides the key to the problem, how much truth there is in solipsism. For what the solipsist means is quite correct; only it cannot be said, but makes itself manifest. The world is my world: this is manifest in the fact that the limits of language (of that language which alone I understand) mean the limits of my world.

It is not how things are in the world that is mystical, but that it exists.

The aim of the book is to set a limit to thought, or rather — not to thought, but to the expression of thoughts: for in order to be able to set a limit to thought, we should have to find both sides of the limit thinkable (i.e. we should have to be able to think what cannot be thought).

It will therefore only be in language that the limit can be set, and what lies on the other side of the limit will simply be nonsense.