If philosophy is good at one thing, it’s pointing out things that seem so obvious we don’t even notice them and making them suddenly seem unnervingly strange. Here’s one: would you rather your best days were ahead of you, or behind you?

For most people the answer is irritatingly obvious. Of course we’d all prefer our best days to be ahead of us. Nobody wants to think they’ve already peaked. That might even seem perfectly rational. After all, if your future is going to be better than your past, your life overall will ultimately contain more goods – it’ll have higher ‘net welfare’ – than it would if things just coast along as they are, or started to decline.

But this is where those weirdly artificial thought-experiments (for which a certain type of philosophy is notorious) really come into their own.

Consider the following scenario from the Oxford philosopher Derek Parfit. You need an operation. The operation is always successful, but it hurts like hell, and you can’t have an anaesthetic. To lessen the trauma, once the operation is over, you’ll be given a drug that wipes your memory of the operation and the hours leading up to it. You wake up in a hospital bed. You don’t remember being wheeled in for surgery, but then, that’s just what you’d expect if you’d had the operation. You ask a nurse if you’ve been operated on yet. The nurse says she knows the facts about two patients, but she’s not sure which patient you are: either you had your operation yesterday, and it lasted for ten brutal hours; or you’ll have the surgery later today, and it’ll only take two hours. Which do you hope turns out to be the case?

Everybody I’ve ever run this scenario past – and there’s been quite a few, which is probably why I don’t get invited to parties much any more – all say the same thing. We’d all prefer to find out we’d had the surgery yesterday.

But think about that for a moment. While the nurse is off finding out, you’re desperately hoping your life contains more overall pain. You’d prefer to have a worse life, one containing eight hours more pain, than the life you’d have if your surgery is tomorrow.

Yes, you might say, of course – because that extra pain is all behind me. But why should that make a difference? Why should pain matter less if it’s in the past than if it’s in the future? We all agree that it does, but actually finding a rational justification for this ‘temporal discounting’ turns out to be maddeningly hard. A bee sting hurts the same on Tuesday as it does on Thursday, regardless of whether today is Wednesday or Friday; so why would I rather be stung yesterday than tomorrow? Parfit’s little thought experiment seems to uncover a deeply troubling fact about us: we’re biased towards the future, a bias that’s so deep we don’t even notice it, a bias that can at least in theory lead us to act against our overall best interests.

Even weirder, this bias works differently depending on whether we’re thinking about our own future or those of others. Philosopher Caspar Hare has even argued, pretty successfully I think, that the bias is different depending on whether we’re near or far from the person whose welfare we’re considering. If I hear about your surgical predicament from a distance, I hope it turns out you had the shorter operation. But if I’m waiting at your bedside with you for the nurse to come back, I hope it turns out you had the (longer) surgery yesterday.

Parfit may have made this asymmetry clear for us, but he wasn’t the first person to realise there’s something lopsided about the way we think about the future. There’s an argument that goes back at least as far as Lucretius, the first century BCE philosopher-poet and follower of the teachings of Epicurus, that makes important use of this thought. For Epicureans, one of the most urgent tasks for improving human life is overcoming the fear of death that bedevils our existence. As Epicureans didn’t believe in any sort of afterlife, to be dead is, simply, to not exist. We didn’t exist before we were born, either – but nobody thinks there’s anything tragic or lamentable about that. We often say someone is “gone too soon”. We never lament that someone was “born too late”, unless we mean that they would have thrived better in an earlier epoch than they do now.

But if I don’t care about the time when I didn’t exist before I was born, why should I care about the time when I won’t exist after I die? Non-existence is non-existence, just as pain is pain. If it makes no sense to get upset about pre-natal non-existence, it shouldn’t make sense to get upset about posthumous non-existence either.

Feel better about death? Yeah, me neither. We care about the future over the past in a way that’s hard to explain and harder to justify, but so deeply ingrained it’s hard to even imagine things being otherwise. If we take a ‘view from no-when’ and consider our lives as wholes, it seems the rational thing to do would be to prefer the life that has the highest overall welfare (whatever that turns out to mean). But from mid-stream, so to speak, we care much less about what’s behind us than what lies ahead. Our lives in time are shot through with asymmetries: nostalgia, relief that something painful is over, fear that something painful is yet to come.

Some philosophers have tried to justify this bias. Maybe we care about death but not pre-birth because death involves a loss of something that already exists. Maybe we care about future goods more than past ones because we take it the future is open and indeterminate, which makes it more urgent than the unchangeable past. Perhaps it’s just an evolutionary hangover: an animal that cares more about securing its future than dwelling on its past is more likely to survive than one that’s indifferent between past and future. In that case, perhaps what’s really surprising is that we care about our past as much as we do.
Our bias towards the future seems to point to a deep division in what we are. Each of us is a human animal, living a life that is spread out across time. But each of us is also a present-tense subject of experience, living here-and-now, relating to events that are been-and-gone or yet-to-come. Sometimes, the interests of those two perspectives will conflict – which is perhaps why you’d take a worse life if you knew the pain was already behind you.