Based on knowledge of external world. Make sense of the external world, through signs, because they're not self evident. In an interaction, we change each other. When a consultant enters a company, the company is immediately changed, as a new person has entered a system. Related with the deep ambiguity of language, words, and meanings, particularly verbal.
Human systems show all types of complexity.
Questions Simon recognizes rationality, but doesn't recognize ambiguity and sensemaking. Literature is distinct. Santa Fe deals with self-organization. Math deals with chaos. All evolutionary systems show emergent properties, but not vice-versa.