This is essentially my undergrad thesis topic, going off of the text On Certainty by Wittgenstein.
Here's a scanned translation:
http://budni.by.ru/oncertainty.html (some minor errors)
It deals, basically, with the linguistic conditions of knowledge and what it means to sensibly doubt something.
I will happily define any of the terms I can understand. One of his master metaphors, for instance, is the "game", or "language-game".
It refers roughly to our usage of language within a culture.
By his definition, everyone who speaks and understands American English is "playing" more or less the same game. I would be in a completely different game than a native Japanese speaker, as they're using a completely different set of rules, even if it is the same foundation(a society of human minds).
Being part of these games is one of his conditions both for claiming to have knowledge and claiming to have doubt. Since language is almost univocal with thought, not participating in a game is the equivalent of relinquishing your status as a thinking human. Distancing yourself from the game, such as was the aim of Descartes Meditations, leaves you unable to sensibly doubt. You are either being ignorant of the presuppositions which tie you to the game, or you are completely silent.
Anyways, see for yourself, and comment if your muse so leads you.