... desire utilitarianism says that moral imperatives can only be known by way of calculations involving billions of (mostly) unknown variables: desires, strengths of desires, relations between desires and states of affairs, and relations between desires and other desires.First of all it is important to note that however complicated this issue appears to be it relies upon only real entities or facts that exist and only of a very few type of entities, namely desires, states of affairs and the relations between them. Luke also adds strengths (of desires) and quantities of desire (holders or agents) to the mix. In an early post when I was first exploring and testing the ideas within the desirist framework I wrote:
When a scientist deals wants to investigate complicated real-world phenomenon, they seek to isolate the key factors and either though laboratory experiments or field studies obtain relevant data to analyse and test against. They examine the factor(s) of interest - the independent variable(s) in terms of their effects on the dependent variable(s) and if their research is valid will find some form of predictable relationships to develop further.Now, as I am beginning to see when I review these old or early posts, this is not quite correct and this post can serve as an update of these thoughts but essence of these thoughts still stands, it just needs some revision but not replacement or rejection.
The same approach can be used here where the factors of interest are now the desires and their measurements is due to their fulfillments and thwarting. When looking at a specific situation of an interaction of two or more agents, lets look to identify the specific types of desire involved. One can factor out the amount - the number of agents - that hold tokens of those desires and also factor out the confounding factors - fulfilling and thwarting not due to the interactions of agents - and look specifically at the desire-desire interactions. This is analogous, somewhat, to population geneticists looking at populations of gene pools rather than populations of individuals.
Now we have these desire-desire interactions, one can evaluate a single desire, call it the independent desire in terms of it's material effects on all other desires whose fulfillments or thwartings are effected - the dependent desires. The independent desire is treated as a means evaluated to the ends (fulfillments and thwartings) of the dependent desires. How does one vary the independent desire? By comparing the dependent effects of its presence versus its absence. The result is a description of the amount of desire thwarting/fulfilling that the dependent desire has compared to its absence.
A common mistake in seeking to understand this approach is to impose an act based framework on this. That is to look at an individual act as primary rather than the collection of instances or token of the type of desire under consideration as primary. The prefix of "desire" in desire utilitarianism is meant to provide a different evaluative focus to act or rule utilitarianism, where the evaluative focus of the latter two are acts or rules respectively. (Others such as Tody Ord or Richard Chappell in advocating what they call global consequentialism talk about motive, rule and act consequentialism, desirism is a form of motive consequentialism - since it argues that desires are the only form of motivation that exist). However when you make the act primary then you end up with desire fulfilment act utilitarianism - that is where the evaluative focus is still on acts and the utility is desire fulfilment and this is a different model and one I, and as far as I know Luke, regard as inferior to desirism (or desire utilitarianism - I also like my new name because it is quicker to type). It, to me, very much looks like the above quote from Luke is, somewhat mischievously (although the comments in his post have missed this), highlighting this error and I regard this more as a statement of an issue with desire fulfilment act utilitarianism and its problems and indeed this is an issue with any form of act utilitarianism.
Now returning to my quote and revising it here, if we think in terms of the type of desire under consideration there are going to be many instances or token occurrences of it, both actual and potential. Following an approach similar to Stephen Toulmin's argument fields model, we can say that there are a number of factors that can vary from token to token but we seek to find what is invariant in each token. This leads us understanding the desire type where we look only at the invariants and this is what is meant by seeking to understand a desires material and physical affects. That is items such as the numbers of holders of the desire under consideration, the number of those affected by this desire, the range of other desires they all have, the strengths of all those desires and how far you go in seeking to discover the material and physical affects, all vary from token to token, what remains in studying the type is the desire-desire interactions without these various individual token weightings. This leads to the same point as in my above quote without a possible misreading of it as a simplification, abstraction or generalisation (or any combination of these). The invariants of the desire (or desire type) under study exist in all the token instances.
So we can see that the supposed issue stated in Luke's above quote is really referencing desire fulfilment act utilitarianism not desire utilitarianism. There are two points required to finish this argument. The first is that many of the most basic and common desires and aversion can be be understood in this way, without requiring the messy details of any token. and one can review, revise, replace or reject any moral intuition - whether your or others - on this basis. Indeed part of the basis for moral intuitions is that is works more as a set of types of intuitions. One can now test to see if these intuitions and/or how and when they are applied (or not) are just prejudices inherited by one's culture and so on.
Finally, of course, there are many real world challenges in identifying what are the relevant desires, especially when more than two agents are pro-actively interacting and so on, but this is a different issue to that indicated the quote from Luke above. The world is a noisy and messy place with many challenges in to establishing the relevant facts but this is so for any empirical enterprise and is no different here. However complicated some situations can be, especially more rare and extreme ones, and long standing ethical controversies such as abortion, euthanasia and so on, for most of the time the above seeking of desire-desire interactions as desires types is far simpler and can suffice to provide the evidential basis for most peoples and societies moral codes and criticisms of existing codes and intuitions.