Cause and effect, the medium of communication. It happens at many levels, molecular bonding, nerve responses, human language, and many more. Communication is the primary driving force of change. It is the way we change in response to communication that is important. When a thermostat gains a few feedback loops, its behavior becomes more and more complex. There's a point where mortals can't predict what its going to do next. We and AI are just complex thermostats.