The Society of Mind is the theory of human intelligence developed by Marvin Minsky.

The Society of Mind theory views the human cognitive system as a vast society of distinct and individually simple processes known as agents. These agents are the fundamental particles from which minds are built, and together produce the many abilities we attribute to minds. The great power in viewing a mind as a society of agents, as opposed to as the consequence of some basic principle or some simple formal system, is that each agent can be based on a different type of process with its own distinct kinds of purposes, languages for describing things, ways of representing knowledge, and methods for producing inferences.

This idea is perhaps best summarized by the following quote from Minsky:

What magical trick makes us intelligent? The trick is that there is no trick. The power of intelligence stems from our vast diversity, not from any single, perfect principle.

-- Marvin Minsky, The Society of Mind, page 308