“We are taught judgments and their connection with other
judgments. A totality of judgments is made plausible to us.”

"I know" seems to describe a state of affairs, which guarantees what is known, guarantees it as a fact. • "I know" is usually understood to mean, "I can't be wrong," that I have "the proper grounds for my statement." • But from the utterance, "I know," it does not follow that he knows it. • It needs to be shown that no mistake is possible. • One can say, "He believes it, but it isn't so," but not, "He knows it, but it isn't so." Does this stem from the difference between the mental states of belief and knowledge? • What is the difference between a mistake and a mental disturbance?

The truth of certain empirical propositions belongs to our frame of reference. • Does one have the right ground for his convictions? • I did not get my picture of the world by satisfying myself of its correctness; nor do I have it because I am satisfied of its correctness. No: it is inherited background against which I distinguish between true and false. • The propositions describing this world-picture might be part of a kind of mythology. And their role is like that of the rules of a game.

My convictions form a system, a structure. • Even my doubts form a system. • I have not arrived at my conviction by following a particular line of thought. • All testing, all confirmation and disconfirmation of a hypothesis takes place already within a system.

We do not learn the practice of making empirical judgments by learning rules: we are taught judgments and their connection with other judgments. A totality of judgments is made plausible to us. • It is not single axioms that strike me as obvious; it is a system in which consequences and premises give one another mutual support.

The child learns to believe a host of things. It learns to act accordingly to these beliefs. Bit by bit there forms a system of what is believed, and in that system some things stand unshakably fast and some are more or less liable to shift. What stands fast does so, not because it is intrinsically obvious or convincing, it is rather held fast by what lies around it. • What we believe depends on what we learn. • The child learns by believing the adult; doubt comes after belief. • The difficulty is to realize the groundlessness of our believing.