The first 65 notes echo the discussion of certainty in Philosophical Investigation pt 2 section XI. The distinctions between psychology and logic which are made there apply in On Certainty as well. For instance when discussing knowing what is happening with other people:
Two points, however, are important: one, that in many cases some-one else cannot predict my actions, whereas I foresee them in my intentions; the other, that my prediction (in my expression of intention) has not the same foundation as his prediction of what I shall do, and the conclusions to be drawn from these predictions are quite different.
I can be as certain of someone else’s sensations as of any fact. But this does not make the propositions “He is much depressed”, “25 x 25 = 625” and “I am sixty years old” into similar instruments. The explanation suggests itself that the certainty is of a different kind.— This seems to point to a psychological difference. But the difference is logical.
“But, if you are certain, isn’t it that you are shutting your eyes in face of doubt?”—They are shut.
Am I less certain that this man is in pain than that twice two is four?—Does this shew the former to be mathematical certainty?——
‘Mathematical certainty’ is not a psychological concept.The kind of certainty is the kind of language-game.
On the next page, Wittgenstein separates a “theory of knowledge” approach of scepticism from the viewpoint of language games:
We should sometimes like to call certainty and belief tones, colour-
ings, of thought; and it is true that they receive expression in the tone of voice. But do not think of them as ‘feelings’ which we have in speaking or thinking.Ask, not: “What goes on in us when we are certain that .. . .?”— but: How is ‘the certainty that this is the case’ manifested in human action?
“While you can have complete certainty about someone else’s state of mind, still it is always merely subjective, not objective, certainty.”— These two words betoken a difference between language-games.
These observations underline how efforts to distinguish between language games is not a search for a substitute for what a “realist” like Moore is sure he has found.