I previously argued that Parfit's affect-based objections to temporal neutrality fail. As Alex pointed out, though, Parfit also offers a more direct objection. As part of the 'bias towards the future', he thinks that we might really prefer to suffer a greater pain in the past rather than a lesser pain in the future. Now, assuming that we cannot affect the past, it is difficult to see what this preference amounts to, at least if it is meant to be distinct from mere affect, e.g. relief upon learning that a painful operation is now past. There is no genuinely possible choice in which the preference could be revealed. But perhaps we can imagine an impossible choice, involving time travel or divine intervention in foreknowledge of one’s backward-looking prayer. Can we then imagine, in this impossible scenario, reasonably choosing to have one’s pains amplified and shifted into the past?
There are two bad reasons why we may be tempted to affirm this. First, we are used to the equivalence between being over and ceasing to extend in time. So a typical preference for a pain’s being over is inseparable from the preference that it become no longer - a preference that the temporal neutralist can clearly endorse. Second, even if we appreciate that in this special case the past pain is no shorter, we may fail to fully appreciate that it is really experienced at all. By the time we are in the present, our past experiences have already been and gone. We did not experience them the first time through, so it may seem that shifting pains into the past is simply a way to make them disappear altogether! Of course, this intuition illicitly reflects our assumption that we cannot really change the past - an assumption that must be rejected in the scenario under consideration (since we are supposed to be introducing pains into the past that would not be there otherwise).
When we take care to avoid these two mistakes, and instead really vividly appreciate the greater pain that our past self really would suffer if we made the relevant choice, does it still seem so obviously preferable?