This brings us to the last of the big three forms of wealth extraction, and the one most associated with critiques of capitalism: profit from production, whether taken by private owners or by shareholders.

In everyday talk we tend to use the word ‘profit’ loosely to refer to any surplus of revenue over costs, regardless of the circumstances in which it arises. If you buy some goods for £10 and manage to sell them to someone else for £15, you might say you’ve made a profit of £5. But for your £5 to have any value, there must be some other goods or services on sale somewhere that you can buy with it, and of course they have to be produced. If producers produce only enough to cover their costs, then there can be no profit. Only if they produce and sell more than this can there be any profit. So, while profits can appear in such exchange of goods for money, the origin of profit in a whole economy can’t be in exchange: it must be in production. For it to be possible for some to make profits systematically by buying cheap and selling dear, somewhere in the economy a surplus of goods must be being produced.

Imagine an economy of small, worker-owned cooperatives producing goods and services for sale in markets. Each cooperative has to decide how much of the revenue it gets from those sales to take as their pay, and how much to invest or save. Whether they call the difference profit or something else, it’s clear that it’s the difference between the value of what they produce and all the costs – wages, buildings, materials, equipment, energy and so on – that go into producing it. If they don’t produce and sell goods or services with a value that is greater than these costs they won’t make any surplus or profit.

But cooperatives account for only a small proportion of businesses today. In a capitalist society, most businesses are privately owned by capitalists – or shareholders, though we’ll come to them later.