A member of the studio audience pointed me to an entry in the Stanford Encyclopedia of Philosophy that contains the following passage critical of desire-based theories of value.
[A desire-based account of reasons for action] has been argued, for example by Parfit, to entail that if my motivational system were unusual enough, I could have reasons to do very odd things such as eating light bulbs; and that if I had a motivational system to which the concerns of morality failed to speak I might have no reason to act morally (Parfit, 2006, 354–355; see also Quinn, 1993; Mele 2003, 79; Heuer 2004, 49–53; and Parfit On What Matters—see Other Internet Resources).
(See: Stanford Online Encyclopedia of Philosophy Reasons, Justifications versus Explanations)
Yes, it is possible for a being to have reason to eat light bulbs.
Imagine a planet in which the life evolved a use for silica – a mineral found in glass. Because of this use, it grew silica-detectors on its taste buds and evolved a disposition to eat (from time to time) an object if its taste buds detected silica.
Ultimately, as this life form grew intelligence and developed entertainment, while out watching a sporting event (for example), they might order spun glass on a stick the same way that humans might order cotton candy.
Now, let us say, a space ship containing a group of these creatures crash lands on Earth. They might well come to see our light bulbs as a kind of lollipop or ice-cream cone.
In the mean time, back on their home planet, there are philosophers dismissing the idea that value is based on desires by arguing, “If my motivational system were unusual enough, I could have reason to do very odd things, such as eating sugar crystals.”
One could argue that I have given these creatures a reason to eat light bulbs because of their nutritional value – because they sustain the life of the creature the way that sugar sustains the life of a human.
However, we eat a lot of sugar even where we do not make good use of the calories that sugar provides. It is certainly not for reasons of maintaining life that we eat sugar. Our reason for eating sugar is often for no reason other than that we have come to enjoy doing so. Similarly, the species that has the same taste for silica that we have for sugar may come to eat a light bulb merely because they like the taste.
There is no objection here to the eating a light bulb that cannot be applied to the eating of cotton candy, for example.
As for the issue:
; and that if I had a motivational system to which the concerns of morality failed to speak I might have no reason to act morally
Well, many people do not have reason to act morally – or do not have sufficiently strong reasons to act morally. This is one of the reasons why there is so much evil in the world.
However, their lack of a reason to act morally does not change the fact that people generally have many and strong reasons to give him a reason (or to cause within him a reason) to act morally. This, in turn, would involve the use of social tools such as praise, condemnation, reward, and punishment as a way of giving people (causing within people) reasons to act morally.
The assumption that everybody automatically has a reason to act morally is entirely unfounded. It is one of those assumptions that could stand a little bit of scrutiny and examination so that we may toss it and look, instead, at what is true in the real world.
In the real world, desires are the only reasons for action that exist, and some people simply do not have good desires (or have particularly strong bad desires). These people lack sufficient reason to do that which a person with good desires would do – reasons that we have reason to give him, because a person with good desires will tend to act so as to fulfill the desires of others.