Diagrams in general are mainly used for illustrating contents. However, the diagrams are also used as tools with which thinkers construct and develop their thoughts. This study focuses on this kind of diagram. In the western culture, diagrams of this kind are mainly seen in the Middle Ages and the Renaissance. For example, the diagrams were used for logical thinking processes, which were treated as the reduction of the syllogisms and the art of mnemonics.  Giordano Bruno was used his diagrams for thinking about harmony of universe (Fig.3). In the eastern culture, the diagrammatic representations were frequently used in order to expound traditional doctorine and spiritual images (Fig. 4,5). In addition, many diagrams were drawn by the thinkers in Japan, especially in the Edo era (17th and 18th centuries).  They represented their philosophical and theoretical ideas in diagrams, and used them in their thinking processes (Fig. 6,7).


Fig.1. (Upper left) The Reduction of Syllogisms by Jean Buridan (14th century)

Fig.2. (Upper right) The Ars Brevis of Ramond Lull (1617)


Fig.3. The Diagrams by Bruno, G. (1558)                      Fig.4. The diagrams of “Tai-chi” (1796)


Fig.5. (Upper left) “Rokurin-Ichiro-no-Zu” by Zenchiku (15th century)

Fig.6. (Upper middle) “Shinpo-zukai” by Banzan Kumazawa (17th century)

Fig. 7. (Upper right) The Diagram in “Todo-shinnden” by Shoeki Ando (18th century)