And yet, also a thermostat is doing nothing else but following a gradient towards a desired state (albeit the gradient is discrete and it's moving along the dimension of temperature).
Except that a thermostat doesn't "follow" anything. It is basically a binary response state: on or off (or high and low). Nothing further. Analog or digital, it doesn't follow anything.... It reacts instantly at a setpoint. Would you think an alarm clock is "following" the time, and turns the alarm on at the set time? Or is it a momentary switch at a setpoint....