Abstract
In this essay, I try to analyze how we use information. It is said that we can get a profit by using information. But information itself is not useful. Usefulness of information depends on how we use it, when it is used in a case which a person and other take part in together. And a person has to examine possibilities of changing not only my judgement but other's judgement. In other words, a person has a surplus way in inferring process to decide a strategy. This fact is important. First, this means that a common views is error. Getting information does not reduce burden for deciding a strategy, because it makes a situation complex. Second, this means that a person has to pay attention to uncertainty of other's judgement through getting information. Information which clears a uncertain factor in a situation forces him to pay attention to more radical uncertainty, other. After all, information decrease uncertainty and simultaneously show new uncertainty. This is a paradoxical character of information.
