Expected values and priors.
Saving someone from being eaten by bears might lead them to conceive the next Hitler, but it probably won't (saith my subjective prior). Even with an infinite future, I assign a substantial probability to hypotheses like:
And so forth. I won't be very confident about the relevant causal connections, but I have betting odds to offer on lots of possibilities, and those let me figure out general directions to go.
This is our monthly thread for collecting arbitrarily contrived scenarios in which somebody gets tortured for 3^^^^^3 years, or an infinite number of people experience an infinite amount of sorrow, or a baby gets eaten by a shark, etc. and which might be handy to link to in one of our discussions. As everyone knows, this is the most rational and non-obnoxious way to think about incentives and disincentives.