For those who haven’t read the novel or seen the film, The Martian deals with one man’s attempt to stay alive after a manned expedition to Mars is forced to make an emergency evacuation from the planet’s surface and leaves him there, believing him dead. Everyone thinks he’s dead. But he’s not, and he immediately has a choice to make: curl up and die, or somehow --- against huge odds --- survive until the next manned expedition arrives, which will not be for several years.
Obviously, he chooses not to curl up and die (we’d have no story if he did, or at least, a very different story) --- a choice that is both rational and irrational at the same time. It’s rational because the imperative to survive is the strongest drive hardwired into every living organism; it’s irrational because, on the surface at least, the odds against him succeeding are so massively overwhelming that it seems ridiculous to even contemplate it. That’s interesting in its way, but because of the innate survival imperative, not particularly remarkable. It’s what happens next that I did find remarkable: when the crew of the Hermes is belatedly informed of the protagonist’s survival (NASA knows long before them), they unanimously make a more or less mutinous decision to head back to Mars and rescue him. It’s doable, but very, very risky in a number of ways, mostly physical, some psychological.
It’s irrational for five people to place themselves in lethal danger so that one person might be saved. (Mr. Spock would raise his eyebrow and solemnly declaim, “Highly illogical.” And he’d be right.)
But... it doesn’t strain credulity, because we see and hear and read about such kinds of situations every day. And that’s a boon when we write stories. Irrationality is the spice we add to the mix of any story.
People behave irrationally. They do so because of reasons both honourable and dishonourable. Love, redemption, altruism, guilt, hatred, jealousy, anger, lust for power, possessions or control --- our emotions are constantly provoking us to do things that, if we stopped and thought calmly for a moment, many of us wouldn’t remotely consider. And that is a gift to writers that’s been around ever since humans began telling stories. For example, Paris, Prince of Troy, abducted Helen, thereby bringing about the Trojan war; Hamlet listened to a ghost who may or may not have been his father make all sorts of accusations that set off a bloody saga of revenge; Jane Eyre believed she had been wronged by Edward Rochester and left his house precipitously, almost eliminating the chance of happiness for them both. Great literature is full of examples of people behaving irrationally. In tragic literature, these irrational actions destroy the people who make them; at other times, the story is about redemption from those irrational actions. Really, no action is too stupid in terms of human behaviour, unfortunately --- something which many people seem more determined than ever to prove nowadays, especially thanks to the internet and social media.
However, we need to take care that a story character’s actions aren’t too “unbelievably” irrational/stupid in the eyes of the reader, because if those actions appear a little too conveniently stupid --- convenient in plot terms, that is --- readers roll their eyes and mutter sceptically, “Seriously?” You can’t make irrationality into a deus ex machina. Well, you can, but as a writer you lose all credibility when you do so. Nor can characters become too irrational, unless they’re deliberately being written as mentally unstable.
So it’s a fine balance: people do stupid things for all kinds of reasons, but as story characters, they can’t be too stupid, because readers lose patience with them. So we just have to stick with it and search for that fine balance.
After all, to do otherwise would be irrational.