This is a talk that I have prepared for the Universidad Carlo III in Madrid tomorrow. It is a summary of recent work that I have been conducting with colleagues at Northeastern, Wisconsin, and Oxford and that I’m beginning to develop into a book manuscript.

In the model that I present, an individual holds potentially connected beliefs about political or moral issues, which we can represent with nodes and links (an “idiodictuon”). Whether and how the various ideas are linked in the person’s network influences that individual’s actions and opinions. When people discuss political or ethical issues, they share portions of their respective networks of which they are conscious at the time and may bring ideas from their interlocutors into their own idiodictuons.

Some network structures are better than others for discussion: overly centralized or scattered networks are problematic. Individuals tend to demonstrate similar network structures on different issues, so that having a proclivity for a certain form of network is a character trait.

People, with their respective networks of ideas, are also embedded in social networks. An idea is more likely to spread depending on features of both the social network and the idea networks of the people who interact. Specifically, the odds that an idea will spread from a given person depend on how many people receive communications from that person and how much they trust the communicator. It is reasonable to take into account the trustworthiness of a source when assessing an idea.

As a whole, a population may develop a shared network structure. An idea that is widely shared and frequently central in individuals’ networks becomes a norm. Such norms play important roles in institutions. A community or a culture is a single network or phylodictuon that encompasses disagreement. Ultimately, all such networks interconnect to form a network of human ideas.