You are casting preference to only extend into the future. I guess that is the largest usage of "preference.". But people also frequently say things like "I wish that hadn't happened to me" so it's also frequently used about the past.

I thought about this, and I agree "regret" wishes like this are clearly possible. We can think of wishes (desires, "wants") as preferences, namely as preferring something we don't have to something we do have. Or more precisely and generally, preferring being certain that something is true to the actual current case of being less than certain that it is true. This means someone can wish that they hadn't been born. Which means they prefer not having been born to the actual case of having been born. More technically, this would mean preferring a certainty (100% probability) of not having been born to the current 0% belief of not having been born.

However, this means we cannot wish for anything we already have. Because that would be preferring having something to having it. We cannot prefer being certain that X is true to our current degree of belief of X being true, if that current degree of belief is such that we are already certain that X is true. In short, we can't prefer being certain that X to our current state of being certain that X.^[1]

Which means I can wish that I had never been born (regret being born), but I cannot wish that I have been born. So it can actually be bad for someone to come into existence, namely when they, after coming into existence, regret having been born (e.g. because of very bad life conditions). But it cannot similarly be good for them to have come into existence, as there is no possible preference of this sort. If they have come to exist, they can't prefer that to having come to exist (as elaborated above), and if they don't come to exist, they can't regret that they didn't come to exist, because someone who doesn't exist can't form any preference, including preferring to exist over the actual current state of not existing.

In fact, this point has been argued before in the context of decision theory. In chapter 4.4 of Richard Jeffrey's book The Logic of Decision he writes (emphasis in the original):

Socrates argues (Symposium, 200) that Love is not a god because to desire something is to be in want of it: you cannot desire what you already have. The point is also made in contemporary dictionaries. Thus, The Concise Oxford Dictionary defines a desire as an unsatisfied appetite, longing, wish, or craving. This account of the matter seems roughly right, although it needs some refinement. Thus, to vary the example of the Symposium, since people do not always know when they are loved, it is entirely possible to desire someone's love when you already have it. Therefore, it seems better to say that you cannot desire what you think you have. Taking propositions as the objects of desire, the doctrine becomes: one who believes that a proposition is true cannot desire that it be true.

I would clarify that strictly speaking you can believe something to be true but still wish it to be true, as long as your belief (as is normally the case) falls short of certainty. Thus, if there is a thunderstorm, you may be 99% sure you won't be struck by lighting, but you can still desire not to be struck by lightning, insofar you (more or less strongly) prefer a 100% certainty not be be struck to your current 99% belief that you will not be struck. Another way of looking at this: if being struck by lightning is "extremely bad", say , then the expected utility of it for a 1% chance/belief is $P (I'm struck by lightning) \times U (I'm struck by lightning) = 1 % \times 1, 000, 000 = - 10, 000$ . Which may still be "very bad".

Of course we can e.g. still wish for (being certain of) things happening in the future, insofar we are not already certain they will happen. ↩︎