There is no reason for longtermists to care specifically about “the far future” (interpreted as our future light cone, or whatever spacetime we can causally affect). Most longtermists probably intrinsically care about all of spacetime across Reality. Even if the probability that we are not in a short simulation is 1e-50, longtermists still have strong reasons to strive for existential security. One of those reasons is that striving for existential security would make all civilizations that are similar to us (i.e. civilizations that their behavior is correlated with ours) more likely to successfully use their cosmic endowment in beneficial ways.
Regarding the part about the outside view argument being also an argument against patient philanthropy: this seems to depend on some non-obvious assumptions. If the population size in some future year X is similar to today’s population size, and the fraction of wealth generated until X but not inherited by people living in X is sufficiently small, then a random person living in X will be able to donate an amount that is similar (in expectation) to the worth of a patient-philanthropy-fund that was donated by a random person living today.
This topic seems extremely important and I strongly agree with your core argument.
There is no reason for longtermists to care specifically about “the far future” (interpreted as our future light cone, or whatever spacetime we can causally affect). Most longtermists probably intrinsically care about all of spacetime across Reality. Even if the probability that we are not in a short simulation is 1e-50, longtermists still have strong reasons to strive for existential security. One of those reasons is that striving for existential security would make all civilizations that are similar to us (i.e. civilizations that their behavior is correlated with ours) more likely to successfully use their cosmic endowment in beneficial ways.
Regarding the part about the outside view argument being also an argument against patient philanthropy: this seems to depend on some non-obvious assumptions. If the population size in some future year X is similar to today’s population size, and the fraction of wealth generated until X but not inherited by people living in X is sufficiently small, then a random person living in X will be able to donate an amount that is similar (in expectation) to the worth of a patient-philanthropy-fund that was donated by a random person living today.