In VNM utility theory, we assign utility to outcomes, defined as a complete description of what happens, and expected utility to lotteries, defined as a probability distribution over outcomes. They are measured in the same units, but they are not the same thing [...] Type (I), as best I understand it, seems to consist of assigning utility to a lottery. Its not so much an axiom violation as a category error
I am indeed suggesting that an agent can assign utility, not merely expected utility, to a lottery. Note that in this sentence "utility" does not have its technical meaning(s) but simply means raw preference. With that caveat, that may be a better way of putting it than anything I've said so far.
You can call that a category error, but I just don't see the mistake. Other than that it doesn't fit the VNM theory, which would be a circular argument for its irrationality in this context.
Your point about f*ing human brains gets at my True Rejection, so thanks. And I read the conversation with kilobug. As a result I have a new idea where you may be coming from - about which I will quote Luke's decision theory FAQ:
Peterson (2009, ch. 4) explains:
In the indirect approach, which is the dominant approach, the decision maker does not prefer a risky act to another because the expected utility of the former exceeds that of the latter. Instead, the decision maker is asked to state a set of preferences over a set of risky acts... Then, if the set of preferences stated by the decision maker is consistent with a small number of structural constraints (axioms), it can be shown that her decisions can be described as if she were choosing what to do by assigning numerical probabilities and utilities to outcomes and then maximising expected utility...
[In contrast] the direct approach seeks to generate preferences over acts from probabilities and utilities directly assigned to outcomes. In contrast to the indirect approach, it is not assumed that the decision maker has access to a set of preferences over acts before he starts to deliberate.
The axiomatic decision theories listed in section 8.2 all follow the indirect approach. These theories, it might be said, cannot offer any action guidance because they require an agent to state its preferences over acts "up front." But an agent that states its preferences over acts already knows which act it prefers, so the decision theory can't offer any action guidance not already present in the agent's own stated preferences over acts.
Emphasis added. It sounds to me like you favor a direct approach. For you, utility is not an as-if: it is a fundamentally real, interval-scale-able quality of our lives. In this scheme, the angst I feel while taking a risk is something I can assign a utility to, then shut up and (re-)calculate the expected utilities. Yes?
If you favor a direct approach, I wonder why you even care to defend the VNM axioms, or what role they play for you.
I am indeed suggesting that an agent can assign utility, not merely expected utility, to a lottery.
I am suggesting that this is equivalent to suggesting that two points can be parallel. It may be true for your special definition of point, but its not true for mine, and its not true for the definition the theorems refer to.
Yes, in the real world the lottery is part of the outcome, but that can be factored in with assigning utility to the outcomes, we don't need to change our definition of utility when the existing one works (reading the rest of your post...
Followup to : Is risk aversion really irrational?
After reading the decision theory FAQ and re-reading The Allais Paradox I realized I still don't accept the VNM axioms, especially the independence one, and I started thinking about what my true rejection could be. And then I realized I already somewhat explained it here, in my Is risk aversion really irrational? article, but it didn't make it obvious in the article how it relates to VNM - it wasn't obvious to me at that time.
Here is the core idea: information has value. Uncertainty therefore has a cost. And that cost is not linear to uncertainty.
Let's take a first example: A is being offered a trip to Ecuador, B is being offered a great new laptop and C is being offered a trip to Iceland. My own preference is: A > B > C. I love Ecuador - it's a fantastic country. But I prefer a laptop over a trip to Iceland, because I'm not fond of cold weather (well, actually Iceland is pretty cool too, but let's assume for the sake of the article that A > B > C is my preference).
But now, I'm offered D = (50% chance of A, 50% chance of B) or E = (50% chance of A, 50% chance of C). The VNM independence principle says I should prefer D > E. But doing so, it forgets the cost of information/uncertainty. By choosing E, I'm sure I'll be offered a trip - I don't know where, but I know I'll be offered a trip, not a laptop. By choosing D, I'm no idea on the nature of the present. I've much less information on my future - and that lack of information has a cost. If I know I'll be offered a trip, I can already ask for days off at work, I can go buy a backpack, I can start doing the paperwork to get my passport. And if I know I won't be offered a laptop, I may decide to buy one, maybe not as great as one I would have been offered, but I can still buy one. But if I chose D, I've much less information about my future, and I can't optimize it as much.
The same goes for the Allais paradox: having certitude of receiving a significant amount of money ($24 000) has a value, which is present in choice 1A, but not in all others (1B, 2A, 2B).
And I don't see why a "rational agent" should neglect the value of this information, as the VNM axioms imply. Any thought about that?