I’m sorry, but this argument seems rather confused to me.
Assuming some upper limit on the cost you’re willing to pay to reduce carbon emissions, your best strategy is to choose the option that provides the greatest reduction for the least personal cost.
No, it’s to choose the best n options, up to the point at which you reach your cost limit. Depending on the limit, and the options you face, n could be 0, or 20, or 100; but there’s no particular reason to think it should be 1.
Of course, assuming a fixed upper bound on willingness to sacrifice runs counter to the idea that the sacrifices you’re willing to bear should depend on the benefits obtained. There are two alternative perspectives you could take here:
From the perspective of what’s best for human welfare generally (which was the basis of my original claim) you simply shouldn’t have such a limit. If the net effect of an option (taking into account opportunity costs) is positive, you should just do it (This applies even if the option is suicide, though the opportunity cost of suicide is probably quite high compared with other ways of promoting human welfare.)
From the perspective of an imperfect altruist, a better way to think about it is in terms of the marginal rate of substitution that you’re willing to accept between your own welfare and others’. This will presumably increase as your own welfare decreases (and is probably the real reason we wouldn’t commit suicide to reduce emissions, even if the benefits to others did outweigh the personal and opportunity costs).
You’ve got to consider opportunity cost and marginal utility.
Agreed. The thing is, the opportunity cost of becoming vegetarian isn’t like the opportunity cost of $5. If I spend $5 on carbon offsets, that’s $5 I can’t spend on something else. If I become vegetarian, I haven’t really used up a resource that I could have done something else with; in fact I’ve probably saved money (maybe I’ve used up a bit of willpower in the process, I’m gonna say the effect is minimal). The opportunity cost of vegetarianism is my direct loss of utility minus whatever utility I can get from the money I’ve saved.
Assuming the costs can simply be summed
They can be, if you denominate them in human welfare. They clearly can’t if you denominate them in dollars, but I never claimed they could be, and my argument doesn’t rest on it.
I think we’re pretty much in agreement. Any remaining differences are either trivial, semantic, or (at the risk of angering the Aumann Gods) “things reasonable people can disagree about”.