@Lustig Andrei,
'Solypsism' cannot be fixed conceptually so therefore it has been rendered incorrect or irrelevant, and plus the jokes etc. etc.
But you can certainly 'see' just how such a theory would come about(even if you don't want to admit it).
However, simply because something cannot be fixed conceptually doesn't make it un-true, you'll notice that much of the conceptual-world is false, being able to prove something is only valuable in as much as you can 'show' to someone else.
I do know exactly what you meant by your first sentence, if you're suggesting that I simply 'go along' with common definition you can save your breath.