Two characters run your thinking. One produces quick answers: impressions, feelings, and impulses that appear without effort. The other can reason, check, and calculate—but it is slower, and it tires.
Because the fast mind speaks first, you often experience its outputs as if they were obvious truths. The slow mind can intervene, but it usually accepts the first draft unless something feels off.
Treat the two “systems” as a useful fiction, not as literal brain locations. The point is functional: fast thinking generates; slow thinking monitors, corrects, and sometimes overrides.
This is why you can snap to a conclusion and still believe you were careful. It is also why self-control feels like work: it depends on the slow system staying awake.
Once you start noticing which character is speaking, ordinary moments—judging a stranger, trusting a hunch—look less innocent.