This paper proposes deep and fundamental structures of communication among persons in a “coexistential” setting. The basic framework for this formalization of communication structures is Leibnizian notions of space and time together with the notion of the Existential Graph by C. S. Peirce and that of the Petri net, more precisely, the occurrence net. The fundamental structures of coexistential communication are then formalized as co-creation of Leibnizian space and time in such a manner that they are used to link the (...) communicated messages, thus establishing the “coexistential atmosphere and field” (“Ba” in Japanese) among the individuals. This framework is then applied to the analysis of theater play communication. Finally, the framework of information edaphology is also introduced to discuss the growth processes of individuals and communities through coexistential communication. (shrink)