David Hume (1711-1776), a Scottish philosopher of the Enlightenment and one of the most important figures in the history of philosophy, provides one of the clearest illustrations of the problem of trust. He writes of two farmers:

Your corn is ripe today; mine will be so tomorrow. 'Tis profitable for us both that I shou'd labour with you today, and that you shou'd aid me tomorrow. I have no kindness for you, and know that you have as little for me. I will not, therefore, take any pains on your account; and should I labour with you on my account, I know I shou'd be disappointed, and that I shou'd in vain depend upon your gratitude. Here then I leave you to labour alone: You treat me in the same manner. The seasons change; and both of us lose our harvests for want of mutual confidence and security.

This is a classic statement of a familiar problem. If I have no assurance that you will help me tomorrow, I will not help you today and we will both end up worse off. Stated in this way, the problem would have been recognised by another philosopher who wrote on the subject, Thomas Hobbes (you can find out what Hobbes thought by looking at Jo Wolff's piece on this website). Yet Hume's solution differs from Hobbes's, and it does so because his conception of human nature is different from that of Hobbes. What philosophers see as a solution to the problem of trust depends, in part, on their understanding of human nature.

Hume took a much milder view of human nature than did Hobbes. For Hume, we have a natural 'sympathy' for others, and are kindly motivated towards those for whom we care (we are inclined to behave 'partially' to friends). However, Hume also recognized that these "unequal affections" contributed to the problems of justice and trust because, just as we are inclined to act in a kindly way towards our nearest and dearest, we are inclined to act less well towards strangers and enemies. The farmers have, he tells us, 'no kindness' for one another, and any willingness to act justly (to give the other his due) must therefore be an 'artificial' not a 'natural' virtue. It is not to be explained in terms of natural inclinations. How, then, is it to be explained?

One solution – one 'artifice' designed to solve the problem of trust – is to rely on agreement; on a social contract backed up by the force of the Sovereign (and this is Hobbes's solution). Hume rejects not only Hobbes' particular account of the role of the Sovereign, but also the whole social contract tradition. Contract, Hume thinks, cannot explain the binding force of our moral obligations because it relies on the obligation that we have to keep our promises. In a classic essay, "Of The Original Contract", Hume argues that the social contract tradition relies on the thought that one ought to obey the Sovereign because one had promised to do so. However, Hume writes, theorists in this tradition 'find [themselves] embarrassed when it is asked, why are we bound to keep our word?'.

In fact, although Hume's criticism applies to ...