Two. Checking the feeling

This one is invisible from outside and it is often the biggest of the four.

It is the internal check. Do I still believe. Did that feel sincere. Was there conviction behind the words I just said. Replaying the moment the thought arrived to work out what you were feeling at the time.

Every check is a measurement of something that has no reading, and every check produces an ambiguous result, because inner states are ambiguous. So the answer is never clean, which is taken as evidence that another check is needed.

It is a mental act rather than a visible one, which is why people can be doing it for hours a day and never once mention it to anybody.