We can treat being indifferent between outcomes p and ¬p as implying utility (degree of desire) zero: U(p)=U(¬p)=0. This is also a provable consequence of Jeffrey’s utility theory where we assume that tautologies have utility zero. Then, insofar preferences can be observed (reports, choice behavior), we can compare the “sign” of desires. If you prefer outcome q to outcome p, and U(p)=0, then U(q)>0. That is, you desire q to a positive degree. Then we can compare desires between different people based on sign (positive, neutral, negative). This rules out utility functions being equivalent under addition of arbitrary constants. It is not the case that for arbitrary constants b, U∗=U+b.
Moreover, humans are neurophysiologically similar to each other. Which makes it plausible that similar behavior indicates similar desires for different people. E.g. similar reactions to equal pain stimuli indicating similar aversion to pain, desire for drinking water after 24 hours without water being similar, etc. If we accept that some desires are likely similar for certain situations, we can use them for interpersonal comparisons. E.g. Alice desires x as much as Bob, Alice desires y two times as much as x, Bob desires y four times much as x, so Bob desires y two times as much as Alice. This rules out equivalence under multiplication with arbitrary positive constants a, i.e. it isn’t the case that U∗=a×U.
The interpersonal comparison problem is similar to the problem of other minds: The fact that other people a structurally similar to us suggests, by inference to the best explanation, that they also have inner lives. The same line of reasoning makes it unlikely for there to be large differences (utility monsters) in desires with similar observable physiological correlates (behavior, brain activity).
Hmm, I guess I also had in mind extensions to other animals, artificial minds, etc.. I don’t think you can use the same argument about similar neurophysiology and behaviour to rule out rescalings for them.
I agree that you can probably rule out arbitrary rescalings between typical humans based on an argument like yours, specifically using brain activity in specific brain regions responsible for desire.
I think other responses could be more or less strong somewhat independently of brain activity, although won’t typically vary too much. For example, some people could tolerate stronger desires (or stronger desires) of a certain kind before acting compared to others, or try harder to or find it easier to mute their responses. Also, some apparent pain responses don’t even require processing in the brain, i.e. the withdrawal reflex, and those could be more or less strong independently of pain intensity. People could interpret pain scales differently, too, so we can’t match pain reports, either.
We can treat being indifferent between outcomes p and ¬p as implying utility (degree of desire) zero: U(p)=U(¬p)=0. This is also a provable consequence of Jeffrey’s utility theory where we assume that tautologies have utility zero. Then, insofar preferences can be observed (reports, choice behavior), we can compare the “sign” of desires. If you prefer outcome q to outcome p, and U(p)=0, then U(q)>0. That is, you desire q to a positive degree. Then we can compare desires between different people based on sign (positive, neutral, negative). This rules out utility functions being equivalent under addition of arbitrary constants. It is not the case that for arbitrary constants b, U∗=U+b.
Moreover, humans are neurophysiologically similar to each other. Which makes it plausible that similar behavior indicates similar desires for different people. E.g. similar reactions to equal pain stimuli indicating similar aversion to pain, desire for drinking water after 24 hours without water being similar, etc. If we accept that some desires are likely similar for certain situations, we can use them for interpersonal comparisons. E.g. Alice desires x as much as Bob, Alice desires y two times as much as x, Bob desires y four times much as x, so Bob desires y two times as much as Alice. This rules out equivalence under multiplication with arbitrary positive constants a, i.e. it isn’t the case that U∗=a×U.
The interpersonal comparison problem is similar to the problem of other minds: The fact that other people a structurally similar to us suggests, by inference to the best explanation, that they also have inner lives. The same line of reasoning makes it unlikely for there to be large differences (utility monsters) in desires with similar observable physiological correlates (behavior, brain activity).
Hmm, I guess I also had in mind extensions to other animals, artificial minds, etc.. I don’t think you can use the same argument about similar neurophysiology and behaviour to rule out rescalings for them.
I agree that you can probably rule out arbitrary rescalings between typical humans based on an argument like yours, specifically using brain activity in specific brain regions responsible for desire.
I think other responses could be more or less strong somewhat independently of brain activity, although won’t typically vary too much. For example, some people could tolerate stronger desires (or stronger desires) of a certain kind before acting compared to others, or try harder to or find it easier to mute their responses. Also, some apparent pain responses don’t even require processing in the brain, i.e. the withdrawal reflex, and those could be more or less strong independently of pain intensity. People could interpret pain scales differently, too, so we can’t match pain reports, either.