You know how books about writing novels and stories always talk about "conflict"? And you eye your delicate love story or strange evocation of an agoraphobic fantasist, and wonder how you're supposed to get the Kalashnikovs or the divorce-court drama in there? I know why it gets said - I know why this issue matters, and matters hugely - but I've never found "conflict" as a term particularly helpful: so often the human dynamics which drive good stories just don't seem to file under that heading.
"Obstacles" is perhaps a more useful term, when we're talking about plot and story, and fits very neatly with the smaller-scale business of fortunately-unfortunately, which keeps the reader turning pages. But an obstacle tend to sound like a one-off: once you've climbed over it, skipped round it or blown it to smithereens, you can forget about it. And, of course, real life - and therefore fiction - isn't quite like that.
So I was pleased to find this analogy emerging as I was trying to describe to an aspiring writer how narrative drive, and a whole story, grows from characters-in-action, from "What do they want?" onwards. I've had fun elaborating my analogy since then (just as I had fun with my analogy for writing a story as being like building a bridge). But it still, I think, makes sense and is helpful. I haven't yet tried to map it onto act-structure of the sort I explored here, in Tinker, Tailor, Soldier, Spy, but meanwhile, here goes:
Think of a main character as a sailing ship setting out to cross the sea from one port to another. There’s the hope or expectation of actual or metaphorical treasure - riches, love, freedom, safety, wisdom - to be won if they get there, and that's the reason for their journey. But there's the fear of shipwreck which can happen at any time: disaster at a well-known danger-point; a storm you can watch approaching for hours; a rock invisible beneath the waves.
As they sail, they must cope with how external things act on the ship/character: winds, tides and currents are analogues for other people and circumstances in your story. Some of those are expected and can be planned for, at least to some extent; some are completely unforeseen. And they may hinder the journey but may instead help it - a contrary wind may force them to tack, but with a following wind the ship may almost be flying. If the ship's becalmed they may have to ration the water or warp their way out of trouble, or there may be pirates or an enemy fleet. And can your character be sure that the treasure will still be there when they reach at their destination? Should they court danger by hurrying to make sure, or take their time in the hope of pick up other treasures on the way?
Besides, not everything that affects the ship, and must be coped with, will come from outside: internally (the main character's psychology or unconscious), there may be sickness on board, or mutiny in the crew. Does the ship itself start to leak or is there a fire? Or do problems or opportunities draw out new strengths or skills which no one knew were there - which opens up new opportunities?
Do internal and external things interact? Does someone get the navigation wrong, and sail on to rocks because they thought they were somewhere else? Or does someone die, and their deputy gets a chance to propose, and lead an expedition ashore which finds ... what? And maybe one day they get news from a passing ship (which they might not have passed if they hadn't been off course) that things back at home, or at their hoped-for destination, have changed, for good or ill.
Any or all of these external or internal things - problems or opportunities, helps or hindrances, good or bad news - may mean that the ship can or should or must change its course. Maybe the journey gets longer, maybe they reach the port but realise they must go further, maybe they change what treasure they hope for. Maybe they should go home? Or maybe destination and treasure stay the same, but they've been blown so far off-course that how the ship will get there must change: what will they encounter now that they must cope with? And when they do reach port, is the treasure still there? Is it what they expected? And do they now want it?
What matters is that the ship is always trying to get somewhere.
Otherwise - if the ship has no journey to make - then, essentially, there is no story. Without a destination and therefore a course to chart and try to follow, a reason to set the sails and grasp the tiller, your ship - your character - will roll about at random. It will have no reason to steer this way rather than that, no way of deciding when to go with the wind and when to tack against it, when to hold to the course and when to make for a different port. It's powerless as the swell and currents take it, prey to those same winds and tides, the mutiny and sickness. And because we, the readers, know that the ship is doing nothing to reach the treasure, we have no reason to keep reading.