Re: seatbelts, I don’t think you need to invoke effects on future reasoning. If I’m understanding correctly, you’re imagining a situation where, after each one-mile drive with no seatbelt, you say to yourself something like “well, I’ve driven all these other miles with no seatbelt, so there’s no reason to wear a seatbelt for this next mile.” The previous decisions then somehow make you even less likely to wear a seatbelt in the future. But even totally absent this effect, where you use the exact same reasoning every time independent of all past and future decisions, if the one-mile risk is below your threshold you’ll never wear a seatbelt. This is a pretty general problem that doesn’t really depend on the particulars of the person or situation (applies to anything where a big important thing can be decomposed into many small unimportant things), so I’m not sure an appeal to practical reasoning will suffice.
Re: the collective, I’ll tentatively suggest something like “the set of people taking the same action as me, maybe up to differences in magnitude.” If I think that donating a million dollars to Charity X would have a non-negligible impact on the world, I guess it shouldn’t matter if I personally donate a million all at once, if I donate a million in many ten-dollar increments, or if I know that 99,999 other people will all also donate ten dollars and I donate the final ten. But I agree that this is still underspecified.
Thanks for reading!
Re: seatbelts, I don’t think you need to invoke effects on future reasoning. If I’m understanding correctly, you’re imagining a situation where, after each one-mile drive with no seatbelt, you say to yourself something like “well, I’ve driven all these other miles with no seatbelt, so there’s no reason to wear a seatbelt for this next mile.” The previous decisions then somehow make you even less likely to wear a seatbelt in the future. But even totally absent this effect, where you use the exact same reasoning every time independent of all past and future decisions, if the one-mile risk is below your threshold you’ll never wear a seatbelt. This is a pretty general problem that doesn’t really depend on the particulars of the person or situation (applies to anything where a big important thing can be decomposed into many small unimportant things), so I’m not sure an appeal to practical reasoning will suffice.
Re: the collective, I’ll tentatively suggest something like “the set of people taking the same action as me, maybe up to differences in magnitude.” If I think that donating a million dollars to Charity X would have a non-negligible impact on the world, I guess it shouldn’t matter if I personally donate a million all at once, if I donate a million in many ten-dollar increments, or if I know that 99,999 other people will all also donate ten dollars and I donate the final ten. But I agree that this is still underspecified.