We become what we do: Aristotle on habit and character

Aristotle (384–322 BC) was a student of Plato and the teacher of Alexander the Great. He wrote on physics, biology, logic, politics and poetry. But one of his most widely read works today is a book about a very human question: how should we live well? It is known as the Nicomachean Ethics, perhaps because it was edited by his son, Nicomachus.

Virtue as a craft

In the second book, Aristotle draws a distinction that seems simple but has deep consequences. Some abilities we have by nature: we do not learn to see or hear; we have eyes and ears and then use them. Virtues work the other way round: we acquire them by exercising them.

We become just by doing just acts, temperate by doing temperate acts, brave by doing brave acts.

His comparison is with the crafts: you become a builder by building, a musician by playing the lyre. Nobody becomes a carpenter by reading about carpentry. In the same way, Aristotle says, nobody becomes brave just by knowing what courage is. They have to practise it, often while afraid, until brave action becomes second nature.

That is why, he writes, it makes no small difference what habits we form from youth: it makes a very great difference, or rather all the difference.

The golden mean

What, then, is virtue? For Aristotle it is a state of character that finds the right measure between two extremes. Courage lies between cowardice and recklessness; generosity between meanness and extravagance. But the mean is not a mathematical average: it depends on the situation. What is courage for a soldier in battle may be folly for a parent carrying a child.

This judgement of the situation is what Aristotle calls practical wisdom (phronēsis): the ability to see what the moment requires. It too, he says, grows with experience.

From Athens to modern psychology

More than two thousand years later, the psychology of habit has found something similar: behaviours repeated in the same context gradually become automatic, until they no longer require a conscious decision. Aristotle went a step further: he spoke not only of actions but of character. For him, being a good person was not one big decision but the sum of many small ones.

Happiness as an activity

The aim of all this work, according to Aristotle, is eudaimonia, a word usually translated "happiness", but which means more "a flourishing life" or "a life lived well". For him happiness is not a pleasant feeling that comes and goes, but an activity: living according to virtue over a whole life. In the first book he writes that one swallow does not make a spring, nor does a single day; likewise, one day or a short time does not make a person happy. This links happiness directly to habit: it is built slowly, through repeated acts, and is measured across the whole course of a life.

How long does it take to form a habit?

The figure "21 days" often circulates on the internet. It does not come from any reliable study. In 2010 Phillippa Lally and colleagues in London followed participants who chose a new behaviour, such as drinking water after breakfast or running before dinner, and measured every day how automatic it was becoming. On average it took about 66 days, but the range was very wide, from 18 to more than 200 days, depending on the person and the difficulty of the behaviour. Missing a single day did not ruin the process. Aristotle would not be surprised: virtue, like a craft, takes time.

Three kinds of friendship

Two whole books of the Nicomachean Ethics are devoted to friendship. Aristotle distinguishes friendship of utility, when people are linked because they help each other; friendship of pleasure, when they are linked because they enjoy each other’s company; and friendship of virtue, when each loves the other for who they are. The first two are common and good, but they end when the usefulness or the pleasure ends. The third is rare and takes time, because, as he says, people must have eaten the "salt" of many days together before they truly know each other. The character of friendships, too, is built through habit.

How to apply it

• Choose one virtue you want to strengthen: patience, honesty, the courage to speak up.
• Find the smallest action that expresses it: waiting without interrupting until the other person finishes; admitting a small mistake; asking a question in a meeting.
• Repeat it on purpose, in similar situations, until it no longer takes effort.
• Ask about the extremes: am I becoming harsh in the name of honesty? Am I staying silent in the name of patience?

Aristotle promised no shortcuts. But his message is hopeful: character is not fate. It is practice, and every day brings a new chance to exercise it, even after a day that did not go well.