The contemporary evidence seems overwhelming. And yet, even today, most people devote some of their lives to others as parents and carers, and many also as volunteers. Prior to the modern world, people frequently led lives governed by custom, duty, compassion, or faith, in societies where there was limited scope for the pursuit of self-interest. So is the overriding pursuit of self-interest a modern phenomenon, or is it rooted in human nature? An extensive division of labour, as we find in the contemporary global economy, presents a practical problem: each individual is dependent upon the assistance and cooperation of a multitude of strangers, and yet needs, intentions, and trust have to be communicated to others who are only met briefly, if at all.
The canonical solution to this problem was offered by Adam Smith : it is market exchange. Give me that which I want, and you shall have this which you want, is the meaning of every such offer [. Of course, what is offered is usually money, and if people are generally reluctant to care for and trust in strangers, they may be generally willing to care for and trust in money.
It is the nature of money, like that of consumption goods such as meat, beer, and bread, that it can only be possessed by one person or corporation at a time: if it is mine, then it is not yours.
Likewise, it is the nature of exchange that it transfers property. So this suggests a hypothesis: could it be that our very dependence on strangers makes us self-interested?
For we can only benefit from them through the use of money, and money can only be used to purchase things that are either mine or yours.
