shouldn’t we always do the pleasurable thing so long as there’s no negative utility and no opportunity cost
The problem with this (I think, I’m not that hot on decision theory) is that you can pretty much never assign an opportunity cost of zero to an activity unless your life depends on it, as would be the case for breathing. For as long as we’re given no reason to believe our life will end at any particular point, you have to calculate your opportunity costs on the assumption that you’ll continue to live. At least, it seems that way in the general case. You could push this too far by assuming you’ll never die, and therefore you’ll perpetually forego short-term gains for some massive payoff you expect to get infinitely far into the future.
The problem with this (I think, I’m not that hot on decision theory) is that you can pretty much never assign an opportunity cost of zero to an activity unless your life depends on it, as would be the case for breathing. For as long as we’re given no reason to believe our life will end at any particular point, you have to calculate your opportunity costs on the assumption that you’ll continue to live. At least, it seems that way in the general case. You could push this too far by assuming you’ll never die, and therefore you’ll perpetually forego short-term gains for some massive payoff you expect to get infinitely far into the future.