Suppose you almost cause a terrible accident. You are driving too fast
down a quiet street and a child suddenly steps out. You swerve and manage
to miss him. You drive on, nervous and anxious, and feeling very lucky
that you did not hit and perhaps kill the child.
It's all a matter of probabilities. In some universes you do hit him
and in some you miss. By taking the action of driving recklessly, you
increase the number of universes in which you kill the child.
Suppose you cause a different accident. You drive into a crowd of
100 children and kill 20. Do you feel relief that 80 survived? No,
you feel terrible that you have taken 20 children from the universe.
The same feeling is appropriate in the first example, the narrow escape.
You decreased the number of children in the multiverse by your actions.
It is irrelevant that this instance of your consciousness happened to
end up in a universe where nothing happened. The multiverse has been
affected, the measure of that child has been reduced. You have killed
children just as surely as in the second example where you drove into
In general, when you do something and you get lucky or unlucky with
regard to the consequences, you shouldn't look too closely at the
particular outcome you saw. Morally speaking your actions spread out
through the multiverse. The fact that the results, good or bad, are
not immediately visible to you does not decrease their reality.
I don't think that this reasoning implies any differences in how we
should make our decisions. We already base them on probabilites and the
multiverse view retains probability based decision theory. However it
does perhaps change how we should view the outcomes and the effects of
what we do.