1. A paper preparation supporting method for acquiring an assertion and a reason to arrange a structure of a paper, comprising: asking a user a question about an assertion of the paper or a reason of the assertion; analyzing an answer from the user to the question; asking a further reason to support the answer if the content of the answer is not judged to be self-evident; preparing a logical structure indicating a logic of the paper in which the assertion and the reason are related according to the answer; and displaying the logical structure.