On Certainty
In the years 1949-1951, Wittgenstein mainly focused on the problem of knowledge and certainty (Wittgenstein 1969, 2, 18, 24, 54, 82, 88; von Wright 1972, 11; Aarnio 1997, 119). Accordingly, he strove to point out the difference between these concepts.
An important starting point for this is the conceptual distinction between knowledge and belief (Hertzberg 1981, 60). According to Wittgenstein, the sentence “I believe..has a subjective truth. It is an expression of a certain belief. It does not need to be argued at all. In its way, the notion of argument does not belong to the “logic” of the belief-game. If, on the other hand, one claims to know something, he has to be able to provide an argument for that statement. This is the distinction from a simple belief.In order to know something, one must be well-informed about the languagegame played with the notion of knowledge. Once one is familiar with that special game, it becomes clear what kind of arguments one should present to support the knowledge-claim. This does not mean that concrete arguments could not be doubted in an individual case. On the contrary, doubting is a natural part of the knowledgegame. This leads us to the problem of justification.
The arguments supporting the knowledge-claim form a kind of chain that must be extended in case someone doubts an argument presented at a certain point. The arguments are like the strands in a rope. The rope must be strengthened every time the twine turns out to be too weak due to additional questions. Still, this process cannot be continued for ever. One who doubts everything does not belong to the game of knowledge. If, for example, I would doubt every mathematical calculation that is made, I am crazy, and no one would say that I have been mistaken. The game of doubt in itself requires certainty. Therefore, arguments and proof of them must have a final point. At some point it must be possible to say “This rope will last” or, as Wittgenstein thinks, we must be able to trust in something.