This is a linkpost for Von Neumann–Morgenstern utility theorem, which shows that one accepts 4 premises if and only if one maximises expected utility. In my mind, all the 4 premises are self-evident. So I do not see how one can reject maximising expected utility in principle. Relatedly, I think the Repugnant Conclusion follows from 3 self-evident premises.
In 1947, John von Neumann and Oskar Morgenstern proved that any individual whose preferences satisfied four axioms [premises] has a utility function, where such an individual's preferences can be represented on an interval scale [which "allows for defining the degree of difference between measurements"] and the individual will always prefer actions that maximize expected utility.[1] That is, they proved that an agent is (VNM-)rational [has preferences satisfying the 4 axioms] if and only if there exists a real-valued function u defined by possible outcomes such that every preference of the agent is characterized by maximizing the expected value of u, which can then be defined as the agent's VNM-utility (it is unique up to affine transformations i.e. adding a constant and multiplying by a positive scalar). No claim is made that the agent has a "conscious desire" to maximize u, only that u exists.
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Completeness assumes that an individual has well defined preferences:
Axiom 1 (Completeness) For any lotteries and , either or .
(the individual must express some preference or indifference[4]). Note that this implies reflexivity.
Transitivity assumes that preferences are consistent across any three options:
Axiom 2 (Transitivity) If and , then .
Continuity assumes that there is a "tipping point" between being better than and worse than a given middle option:
Axiom 3 (Continuity): If , then there exists a probability such that
where the notation on the left side refers to a situation in which is received with probability and is received with probability .
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Independence assumes that a preference holds independently of the probability of another outcome.
Axiom 4 (Independence): For any and (with the "irrelevant" part of the lottery underlined):
if and only if
In other words, the probabilities involving cancel out and don't affect our decision, because the probability of is the same in both lotteries.
Maximizing expected utility is not the same as maximizing expected value. The latter assumes risk neutrality, but vNM is totally consistent with maximizing expected utility under arbitrary levels of risk aversion, meaning that it doesn't provide support for your view expressed elsewhere that risk aversion is inconsistent with vNM.
The key point is that there is a subtle difference between maximizing a linear combination of outcomes, vs maximizing a linear combination of some transformation of outcomes. That transformation can be arbitrarily concave, such that we would end up making a risk averse decision.
Thanks for the comment, Karthik! I strongly upvoted it. I have changed "expected value" to "expected utility" in this post, and updated to the following the last paragraph of the comment of mine you linked to.