Crucially, even after all such attempts at justification failed, most subjects still stood by their intuition: 'It's just wrong!' What's going on here? Sauer's plausible diagnosis is that these subjects are recruiting System II's intellectual horsepower in service of their intuitive judgments, without engaging the intuition-questioning capacities of System III.

The typical subject would try to justify their intuition that the act is wrong by pointing to some harm it would cause, only to be reminded by the experimenter that, as the case was described, the relevant harm would not occur. Haidt presented subjects with descriptions of harmless violations of moral taboos: for example, two siblings having consensual sex with contraception. Sauer points to Jonathan Haidt's studies on moral dumbfounding (Haidt 2001) as a paradigm case (29-31). The rationalizer uses conscious, complex reasoning to defend her preexisting view (System II) while failing to subject this view itself to reflective, critical scrutiny (System III). The best evidence for the psychological reality of this distinction comes from cases of rationalization. In a slogan: System II is clever, but it needs System III to be wise. Sauer calls this 'System III.' System III's main job is to perform intuition override: to call an intuitive judgment into question, direct System II to critically reflect upon it, and - if reflection shows the intuition to be unjustified - overturn it (2). Hence the need for the second sub-process, which monitors and guides how System II's processing power is used. This is the kind of cognitive functioning measured by intelligence tests: 'System II houses raw processing power, with little or no regard to how that power is used' (21-22). One sub-process, which retains the name 'System II,' enables us to activate, sustain, and manipulate representations in working memory. Sauer argues that we need a further distinction, originally proposed by the psychologist Keith Stanovich (2011): 'System II' is composed of two dissociable sub-processes. Famously, Kahneman divided the cognitive mind into two parts: System I, a bundle of automatic, unconscious, modular processes that generate fast intuitive judgments and System II, the system we use to reach judgments through slow, conscious, effortful thought. Though it is named after Daniel Kahneman's Thinking, Fast and Slow, the central thesis of Hanno Sauer's book is that Kahneman's distinction is too crude.

Thinking fast and slow book review