Thinking (1981), Hare illustrated the two extremes. The "archangel" is the hypothetical person who has perfect knowledge of the situation and no personal biases or weaknesses and always uses critical moral thinking to decide the right thing to do. In contrast, the "prole" is the hypothetical person who is completely incapable of critical thinking and uses nothing but intuitive moral thinking and, of necessity, has to follow the general moral rules they have been taught or learned through imitation. It is not that some people are archangels and others proles, but rather that "we all share the characteristics of both to limited and varying degrees and at different times." Hare does not specify when we should think more like an "archangel" and more like a "prole" as this will, in any case, vary from person to person. However, the critical moral thinking underpins and informs the more intuitive moral thinking. It is responsible for formulating and, if necessary, reformulating the general moral rules. We also switch to critical thinking when trying to deal with unusual situations or in cases where the intuitive moral rules give conflicting advice. Preference utilitarianism Preference utilitarianism entails promoting actions that fulfil the preferences of those beings involved. The concept of preference utilitarianism was first proposed in 1977 by John Harsanyi in Morality and the Theory of Rational Behaviour, however the concept is more commonly associated with R. M. Hare, Peter Singer, and Richard Brandt. Harsanyi claims that his theory is indebted to: Adam Smith, who equated the moral point of view with that of an impartial but sympathetic observer; Immanuel Kant, who insisted on the criterion of universality, which may also be described as a criterion of reciprocity; the classical utilitarians who made maximizing social utility the basic criterion of morality; and "the modern theory of rational behaviour under risk and uncertainty, usually described as Bayesian decision theory." Harsanyi rejects hedonistic utilitarianism as being dependent on an outdated psychology saying that it is far from obvious that everything we do is motivated by a desire to maximize pleasure and minimize pain. He also rejects ideal utilitarianism because "it is certainly not true as an empirical observation that people's only purpose in life is to have 'mental states of intrinsic worth'." According to Harsanyi, "preference utilitarianism is the only form of utilitarianism consistent with the important philosophical principle of preference autonomy. By this I mean the