Das Spiel des Zweifelns selbst setzt schon die Gewißheit voraus. - 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. (5.62)

The agreement or disagreement or its sense with reality constitutes its truth or falsity.

the conditions for sense rather than nonsense in combinations of symbols;