Psychology is contingent
Our dispositions to value things might have been otherwise than they actually are. We might have been disposed, under ideal conditions, to value seasickness and petty sleaze above all else.
Does the dispositional theory imply that, had we been thus disposed, those things would have been values? That seems wrong (Lewis 1989).
According to Lewis’s view, for something to be a value is (nearly) for it to be such that we would desire to desire it under conditions of full imaginative acquaintance. This Lewisian view is a nice example of a dispositional theory of value. In general, dispositional theories of value are theories according to which being a value is identified with some dispositional property – typically a property of the type, being disposed to elicit response R in us in circumstances C.
A dispositional theory of a particular value F (say, beauty or moral rightness) will have the same structure: it will say that being F is being disposed to elicit R in us in C. (Egan 2012).The things that count as values are those that we are actually disposed to value, not those we would have valued in the counterfactual situation. Thus, in a possible world where we are disposed to value seasickness and petty sleaze, these things are not really valuable; even in this possible world, the things that are genuinely valuable are those things that our dispositions in the actual world pick out. While this move reduces the traditional worry that our responses are only contingently rational, it does not make the worry go away. For we can still ask, “Will our actual dispositions converge under ideal conditions?” If not, then we are still confronted by relativism. But at this point, the response-dependence theorist will say, “It may be true that our dispositions are contingent and variable; but you cannot merely assume that they are contingent and variable under ideal conditions.
If we suppose that our dispositions would converge under ideal conditions, then the response dependence conception of morality is quite plausible” (Randel Koons 2003).The point of Lewis' argument is thus that in virtue of their reference to human responses or capacities, the theories under consideration imply an untoward kind of relativity in their respective subject matters. Our response is to accept that this kind of relativity is a consequence of the theories concerned, but to deny that it is untoward. We make two main points in support of this conclusion. The first, as usual, is that the characteristic of causation thus identified is already a fairly non-problematic feature of color and the other classical secondary qualities. It is something we live with in those cases, and may be expected to accommodate ourselves to in the case of causation.
Secondly, however, we want to point out that there is an important difference of degree between the two cases. As we shall explain in a moment, it turns out that causation is very much less sensitive than color, say, to the accidents of the human situation. …