We need the social sciences, but the media does not provide them. I say this because of a recent tweet by Frances Coppola:

If there is one thing we should learn from Auschwitz, it is that atrocities are committed by ordinary, nice people with the full support of other ordinary, nice people.

This contains an unpleasant truth, captured by Hannah Arendt's phrase "the banality of evil": at least some of the perpetrators of the greatest crime in history were just very ordinary men.

But this is an extreme manifestation of a general truth, which is the essence of social science - that social events are not the simple product of individual character. History, said Adam Ferguson, "is the result of human action, not of human design." His contemporary Adam Smith thought that the invisible hand would at least sometimes cause selfish men to act in the public interest:

It is not from the benevolence of the butcher, the brewer, or the baker that we expect our dinner, but from their regard to their own interest. We address ourselves, not to their humanity but to their self-love, and never talk to them of our own necessities but of their advantages.

Conversely, Marx thought that competitive forces would cause even decent capitalists to endanger their workers:

Capital is reckless of the health or length of life of the labourer, unless under compulsion from society...But looking at things as a whole, all this does not, indeed, depend on the good or ill will of the individual capitalist. Free competition brings out the inherent laws of capitalist production, in the shape of external coercive laws having power over every individual capitalist.

Smith and Marx's disagreement hides a common idea - that social facts are the product of complex mechanisms, not individual character.

Indeed, very often individuals' intentions can prove self-defeating. If everybody tries to save more, aggregate incomes fall and so we save less. If everybody tries to work longer in the hope of getting promotion, we all slog ourselves without changing our job prospects. If each individual capitalist tries to raise profits by cutting wages, aggregate demand falls thereby cutting profits. And so on.

But there's more. Individuals' personality and preferences are themselves at least partly socially constructed. As Robert Frank shows in his new book, Under the Influence, our behaviour and ideas are shaped by our peers. Such apparently different events as riots or stock market crashes are caused by information cascades - sometimes ones in which the blind lead the blind. We are also shaped by history. And as Ben Friedman showed and subsequent events have proven, economics also matters: hard times, at the margin, dispose people to become more intolerant, anti-democratic and nationalistic.

The task of the social sciences is to illuminate all these effects. But there is a bias against the social sciences in the media - a bias which is not necessarily intended or even conscious. (What was that I was saying about events not being the product of character?) I'm thinking of five separate(ish) things here:

- The news underplays slow but crucial changes. If you're anti-capitalist you can cite the productivity stagnation as an example here; if you're pro-capitalist, the decline in global poverty in recent decades.

- Journalists prize human interest stories. But this can efface the sociological imagination. And it can lead to a kneejerk response to any event: "whose to blame?" For example, the financial crisis and CEOs' high pay are blamed on greed. This ignores the fact that almost all of us are greedy much of the time, and yet crises occur only rarely and only a few of us earn millions - a simple fact which tells us to look for other explanations.

- Journalists, especially perhaps on TV, try to describe what they see. But the essence of the social sciences is that there are countless mechanisms which are unseen, and invisible. To take an example from today, the BBC reports that dissatisfaction with democracy is at a record high. Public opinion can be measured and seen. But the reports tells us little about why this might be, and ignores Friedman's important point that economic stagnation breeds anti-democratic sentiment (pdf).

- The best journalism invokes a distinction between fact and values, encapsulated by C.P. Scott's maxim, "comment is free, but facts are sacred." This leads to a distinction between factual reporting and opinion - between descriptions of what is happening and of what should happen. This distinction, though, gives too little place to the question: why is this happening? Newspapers employ too many moralists and not enough scientists.

- A concern with facts can deflect attention from mechanisms. Take, for example, the BBC headline, "Brexit deal means '£70bn hit to UK by 2029'". What matters here is not the precise number; this merely invites the retort: how can they possibly know that?" Instead, what really matters are the mechanisms - that frictions to trade can impede growth and, worse still, gradually slow down productivity growth.

It is in these senses that we can speak of BBC bias. Bias doesn't arise merely from bad journalism or individual ill-intent. It also does so from the fact that journalism and social science are two different things.