Certainty

“If you know that here is one hand, we’ll grant you all the rest.” This deceptively simple proposition opens On Certainty by engaging with G.E. Moore’s famous “proof” of the external world. Moore claimed to know with certainty that “here is one hand” — but Wittgenstein asks: what does such knowledge really rest upon? The statement functions as a conditional surrender — if we accept certain basic propositions as known, the entire edifice of knowledge follows. But this reveals that our knowledge system requires starting points that are not themselves justified by other knowledge. ...

“If you tried to doubt everything you would not get as far as doubting anything. The game of doubting itself presupposes certainty.” This is perhaps the most devastating critique of Cartesian skepticism ever formulated. Descartes attempted to doubt everything to find an indubitable foundation — but Wittgenstein shows this is structurally impossible. Doubt is not a freestanding activity. To doubt X, you must hold Y fixed. To doubt Y, you must hold Z fixed. The “game of doubting” requires pieces that don’t move. There is no view from nowhere, no Archimedean point from which all can be questioned. ...