This week we're asking whether it's rational to be optimistic—which seems like bit of a crazy question if you've been reading the news lately. After all, what could possibly justify the belief that everything is going to turn out fine?

Maybe you don’t think everything is going to turn out fine; but you might still think it rational to be optimistic about some things. That might require temporarily bracketing some of those pessimism-inducing headlines—about climate change, women’s rights, or the future of democracy—and starting small. It certainly seems reasonable for some people to be optimistic about, say, having a home, teaching some interesting classes, and enjoying the company of good friends.

You might think cases like that are just a matter of common sense, not optimism: you have good evidence that your house probably won't fall down between now and January 1. But there's a set of more interesting cases, cases where you don't have strong evidence either way. 

Let’s say you take up a new career, like acting. You’ve performed in school plays and done all right, but you’ve never tried to make a career of it. Does it make sense to believe you’re definitely going to succeed? Some might say you’ll never succeed if you don’t believe in yourself, in which case of course it makes sense to be optimistic. (How else could you become the next Daniel Craig?) At the same time, if you quit your day job to chase the Hollywood dream, your chances of success would be low to infinitesimal, and the risk would likely come at a serious cost. It may actually be smarter to be pessimistic about your prospects.

But maybe becoming an actor is a bad example, since you’re unlikely to succeed no matter what you do. And there are some examples that are bad in the other direction, where your chances of success are so good that it’s hard to mess them up. What’s really interesting is the set of cases in the middle, where you stand a real chance of success, but only if you believe in yourself. Instead of trying to star in the next Bond movie, go for the lead role in community theater. That’s still challenging, but you can probably do it—if you have the confidence to really try.

So: set yourself an aspirational target, believe in yourself, and give it a go? That sounds pretty good—but there's still a downside. If you do all that and still don’t get the role, it can be pretty demoralizing. Not becoming the next James Bond is one thing; but not even getting on stage at the Christmas pageant?

It would be great if you could get more information before plunging in, so you can make a smarter choice. But the only way to know how much you're capable of is to try it out. So you're stuck with two imperfect options: do nothing and risk regret, or do something and risk disappointment. It's almost enough to make you side with Samuel Beckett, whose characters are constantly talking about how cruel hope is. Or with The Audience, who wittily sang that "a pessimist is never disappointed."

Almost. But not quite. Maybe it's OK to be a pessimist when it comes to your success on the stage. But what about those big problems we mentioned earlier: climate change, women’s rights, the future of democracy? If nobody believes it’s possible to make a difference there, then nobody will do anything, and we’ll really be doomed.

Of course in a case like climate change, optimism isn’t the solution—it’s arguably part of the problem. People think it won’t affect them, or that somebody else will take care of it, and so they don’t bother to do anything. They take a dangrously sunny view of the future (no pun intended). But is that optimism or just complacency? And is there a difference between the two?

Our guest, Jennifer Morton from the University of Pennsylvania, surely has some thoughts on all this. She's the the author of “Resisting Pessimism Traps: The Limits of Believing in Oneself.”