(i.e. symbolic notation) of logic, especially that of predicate logic, which was still very new during his lifetime and which he himself played a major role in developing, to be philosophically unsatisfactory, because the symbols had their meaning by mere convention. In contrast, he strove for a style of writing in which the signs literally carry their meaning within them - in the terminology of his theory of signs: a system of iconic signs that resemble or resemble the represented objects and relations.

Thus, the development of an iconic,