A story is ultimately not what happens in the writer’s mind that makes her or him write down a series of words. Rather, it is what a given series of words causes to happen in the reader’s. It is only by seriously examining the things we can’t make happen in the reader’s mind that we begin to gain fine control over what we can. For example, there is no way, with words, to make a reader see the color red, but we can make the reader remember the color. ~ Samuel R Delany, About Writing
We want to believe in people. The human mind is exceptionally good at creating characters where there are none. Anthropomorphic personification is a natural, extraordinary power. As Delany says, ‘any two facts and a single pronoun’ start to build a character in the mind. The trick is to make that character memorable, make them real and present. This has little – if anything – to do with appearance. It’s all about the setting of the mind, to go back to last week’s lesson, and the exhibited behaviour of the character.
Physical / Psychological Veracity
From casual observation of the people around us, there are certain things we expect to go together – hunched shoulders and shyness, for example. If your characters stand out from those expectations too strongly, and you don’t explain why – don’t make it believable that they look and behave in such a way – then they won’t feel real to the reader.
Delany makes the point that the list of character traits that make up a heroic figure are pretty rare, so it takes a lot of work and thought to make the fictional hero believable. To some extent this depends on the story and the genre, but I do think it holds an element of truth. It also suggests why the Reluctant Hero trope is so strong – someone willing to dive straight into situations that require a hero is so unusual as to be unbelievable.
Purposeful, Habitual, Gratuitous
These are the types of behaviour that people exhibit, according to Delany. Things they mean to do, things they always do, and things they do because they can. Each one is very revealing of personality, by showing rather than telling. If your character does all three, it helps realise them more fully as a person. That said, the more detail you go into, the more your character starts to sound like everyone else (to paraphrase Oscar Wilde). You need to allow the reader space to fill in the details and make the characters uniquely real to them.
There is nothing so beautiful as that which does not exist. ~ Paul Valery
Context and Contrast
One technique for bringing a character to life is via another character. How do their contemporaries see them? This can be used to show what is the cultural norm, barely remarked upon by those who are used to it, and what is unusual. It can also provide a viewpoint for the character which the reader is still able to disagree with. In real life, we don’t like people because we are told we should; we judge them on their behaviour and draw our own conclusions. That freedom can be very powerful in making the character on the page seem real.
It also provides a very natural way to reveal a character. Rather than dumping an impression all at once, we can get to know one character as someone else does. That then can let the reader apply an improved understanding to earlier passages, changing their impressions with a type of psychological reverse-engineering.