His main idea is that our cognitive functions are executed by two different systems: The first one (system 1) is automatic, fast, doesn’t require much energy, and isn’t very exact (to say the least). The second one (System 2) has to be called explicitly, takes a lot of energy, and its results are much more accurate than those of system 1. This by itself is very interesting, but on top of that, we are limited by the amount of time System 2 can be used until it becomes tired and starts making mistakes. And system 2 can concentrate on only one thing at a time, as is shown by the “Invisible Gorilla” experiment. Are we really that dumb???