Abstract
Deduction by a computer studied so far has been centered around symbolic reasoning with formulas. Recently, attention has been directed to reasoning with diagrams as well, in order to augment the deficiency of reasoning with symbols only. In this paper, we propose a hybrid reasoning system with diagrams and sentences, called JVenn, having perspicuity of diagrams and strictness of symbols complementarily. JVenn is unique particularly in the points that it has the strategy for proving a chain of syllogisms, allows for interplay between diagrams and symbols, and guides reasoning with the beauty measure for diagrams.