Almost everyone is less rational than they believe, especially about themselves

Greene opens with a foundational claim: people consistently overrate how rationally they think and act, particularly in emotionally charged situations, while readily spotting irrationality in others. This asymmetry — clear vision outward, blurred vision inward — is one of the most consistent patterns he identifies across historical and contemporary examples.

He traces this to how emotion actually works in decision-making: strong feelings like anger, fear, or desire hijack judgment first and get rationalized as reasoned conclusions after the fact, so a person genuinely believes they arrived at a decision logically when emotion drove it from the start. The rationalization is often so smooth the person deceiving themselves has no idea it's happening.

Greene's practical response isn't demanding constant emotional suppression, which he considers unrealistic and even counterproductive. Instead he recommends building in delay — noticing when strong emotion has been triggered and deliberately postponing major decisions until it settles, treating emotional intensity itself as a signal to slow down rather than trust your first read.

Takeaway: the moment you feel most certain you're being rational is often the moment you're least equipped to check.