So, I went to the nurse this evening and she had blood test results for me which say that I’m not diabetic. Which is quite the relief, since for the last month — since the notion that I probably am diabetic has been in the air — I’d been living as if I was. Not snacking on any carrot cake or tarte au citron that’s been in my vicinity, avoiding cappuccino with powdered chocolate sprinkles, that kind of thing.

For a month though, I’ve had insight into how a diabetic thinks. Or at any rate, how the diabetic version of me thinks. And that was an interesting experience, confirming a long held model of how beliefs work. Robert Anton Wilson put it thus: ‘what the thinker thinks, the prover proves.’ That is, you hold in your mind a hypothesis, and you’ll sure as hell find evidence for it.

And that aphorism, heuristic, whatever you want to call it…is a good one to bear in mind when you’re developing characters. I am no fan of composing quasi-Freudian biographies tracing the influence of bottle feeding on infant detectives — too easy to produce reams of irrelevant guff, and fall into the trap of believing it whether or not it’s useful for the story. But I do like a good shorthand for getting across a character’s internal processes, since that will provide valuable clues about their behaviour, which is the bit of them we have access to when we see them on screen.

This week’s episode of The Street featured an alcoholic character whose entire personality revolves around drink. Things changed for him when he discovered he was a father. Given something that mattered more to him than waking up in his own vomit, his behaviours started to change — but the years of alcoholism were still a big part of who he was. The tug of war between the different aspects of his character made for strong drama, particularly given that the mother of his son had pretty much written him off — she served to some extent as a means of dramatising his inner conflict.

Note that systems of belief and perception are intricately tied together and self-perpetuating. The nature of drama is about changing a character’s perceptions/beliefs so that they can then act in a new way. This is all about liminality; the dance at the borders of consciousness, which can become a journey to a wider understanding or can result in someone confirming that their existing borders work perfectly well, thanks. Films are about the former, much television writing shows people meandering round the latter territory, since most series are about keeping their characters just so. Can’t have House mellowing and opening a bakery, or Captain Jack letting someone else fight the good fight when he’s first in line for intergalactic scraps and shags.

The trick with writing characters for television is to give them enough variance within their parameters that a range of responses is possible. Whereas a film character can be boiled down thus: they will respond differently to a given stimulus as the end of the film than they did at the start. Which might sound kinda clinical, but is a useful rule of thumb when developing a screenplay: if it’s not true, then something is probably amiss with your protagonist.

Structurally, such issues are to be found at the inciting incident and resolution of stories, to be technical. Someone who uses a gun at the start of the story holsters it at the end. Someone who blushes, learns to kiss. And so on. The thing is, lining up the character beliefs with the action of the story, to ensure that character is what’s driving the plot, and not something incidental to it.