Trying to decide how intrinsic prescriptivity that does not exist can cause an intentional action in the real world is about like trying to determine how many imaginary angels can dance on the head of a pin.
The reason we need to be confirmed about the former case is in order to refute the claim that intrinsic prescriptivity exists and can cause intentional action.
In my last post, I identified three possible routes from intrinsic prescriptivity to intentional action.
(1) Intrinsic prescriptivity can link to action independent of the agent's belief or desire (which raises problems with the ownership of the action).
(2) intrinsic prescriptivity can link to action through a motivating belief that "X is good" which introduces a whole new type of entity - beliefs with motivating power - into our ontology and still leaves the question of what "X is good" means unanswered..
(3) intrinsic prescriptivity can link to action through 'correct' desires - desires that take as their object that which has intrinsic prescriptivity which runs into the problem that desires (like height, weight, eye color, and other evolved traits capable of being influenced by environmental factors) are neither 'correct' nor 'incorrect'.
Walter Sinnott-Armstrong in "Mackie's Internalisms" comes up with a much longer list.
- Fact internalism: Moral facts have some special force built into them.
- Judgment internalism: Moral judgments (as mental states or acts) have some special force built into them.
- Knowledge internalism: Moral knowledge has some special force built into it.
- Acquaintance internalism: Acquaintance with moral facts has some special force built into it.
- Justified-belief internalism: Justified moral beliefs have some special force built into them.
- Thought internalism: Normative thoughts have some special force built into them.
- Belief internalism: Normative beliefs have some special force built into them.
- Seeming internalism: Moral seemings have some special force built into them.
- Seeming-judgment internalism: Moral judgments that seem true have some special force built into them.
Walter Sinnott-Armstrong presents this list of internalisms in his article "Mackie's Internalisms" (from Joyce, Richard and Kirchin, Simon (eds), Philosophical Studies Series, World Without Values: Essays on John Mackie’s Moral Error Theory).
It sometimes seems as if Sinnott-Armstrong is criticizing Mackie for not specifying the type of “intrinsic prescriptivity” he is arguing against. Yet, it seems that Mackie has an easy defense go this charge. “I am criticizing all of them. Look, I could have selected one of these and said that this is my target. However, this means that all of the others would still be unchallenged with its supporters shouting, “What about me?” None of these forms are gong to work, so I am targeting all of them.”
Be that as it may, The conclusion of Sinnott-Armstrong's argument is that the view that Mackie is criticizing is either seeming or Seeming-Judgment internalism. What doesn't exist, according to Mackie, is a "normative reason to do X" or "not to do X" built into actions such that whenever it seems to be the case that something has this property, the agent is motivated to perform or to avoid that action, respectively.
It seems easy to link "seeming" to motivation in a way that Mackie would approve of. An agent interprets her own desire-based motivation to perform an act as "it seems that the object of evaluation has an intrinsic prescriptivity."
This interpretation is incorrect.
Whereas this error is built into the meaning of moral terms, all moral claims are claims about intrinsic prescriptivity from what is, in fact, merely a personal preference.
Mackie would have us end this practice of taking personal likes and dislikes as signs of intrinsic prescriptivity and then taking the fact that others have different interests as evidence that they are, in some way, defective or relating to the world incorrectly. They are not. They are just different.
At this point I would like to add that Mackie does not say that these interests cannot be evaluated. However, that evaluation does not consist in determining whether or not the objects of desire have intrinsic prescriptivity. The evaluation looks at whether the desire tends to fulfill or thwart other desires. Mackie would argue that, where desires come into conflict, we should seek some sort of compromise. I would argue - against Mackie and in support of John Stuart Mill - that morality involves the use of social tools such as reward and punishment to bring to bring private interests and desires into harmony with the public good.