If someone were to claim that market behaviour was peripheral to life in eighteenth century England, it would be easy to laugh at him. This is not to say the claim has not been or will not be made. But if it were made, it could be refuted with a mass of government and private statistics, of newspaper reports and law reports, of high literature, of sermons, speeches and letters, of descriptive and analytical surveys, of biographies and novels, and of physical remains. Ludicrous claims can always be based on selective and misread evidence. In this case, the weight of the evidence must be decisive.

If we turn, however, to the ancient world, the evidence must almost always be indecisive. Very few ancient writings have survived. Obviously, two thousand years are a long time; and ancient civilisation did collapse. Add to this that far fewer documents relating to economic matters were produced or could be preserved than has been the case with us. There was no printing: everything had to be copied by hand. The best writing material was papyrus, which was both expensive and fragile. The normal writing materials for accounts and administrative documents were waxed tablets, which were scraped and reused, and thin wooden sheets, which were thrown away once they had served their purpose.

The literary remains of Greece and Rome which have come down to us through generations of copying and recopying are the products of a rather snobbish culture, and contain little direct information about economic behaviour. The great writers, as Finley observes, do seem to have lacked the conceptual framework for intelligent discussion of finance and commerce. Even otherwise, these were matters they regarded as beneath the notice of history. Thucydides, for example, gives full discussion to the political causes of the Peloponnesian War, but says nothing of what we know from the archaeological evidence was the complete Athenian displacement of Corinth in the pottery markets of the Western Mediterranean world.

During the past century or so, the rubbish dumps of Egypt have revealed a mass of the everyday documentation we have for no other area of the ancient world. There are tax records, and commercial correspondence, and administrative commands, among much else. The problem here is that Egypt was always an exception. From its earliest history, its geography opened it to capture and exploitation by rent-seeking élites. The Pharaohs were worshipped as gods and given whatever they demanded. The Ptolemies organised the country into one gigantic state enterprise and used the proceeds for making a big noise in the Hellenistic world. The Roman Emperors kept up the monopolies and requisitions, treating Egypt as their personal property, and so far as possible isolating it from the rest of the Empire. The documentary evidence, therefore, we have from Egypt may not be representative of the ancient world as a whole.

But this, plus the material archaeology, is all we have. And if we want to know anything for economic motivations and behaviour, we must press the evidence we have as hard as we can. The history of the ancient world is, in many important respects like a mosaic that has been broken up with many of its tiles thrown away. The whole must be reconstructed from the parts remaining. It is a difficult enterprise, but it can be attempted.

If there is little direct, there is much indirect evidence. This is scattered through the surviving body of ancient literature. It consists of casual remarks, illustrations to arguments, even comments that are in themselves foolish. It is a question of looking for this evidence, and of knowing how to use it.

An interesting example of how evidence can be extracted and used comes not from our own ancient world, but from pre-Columbian South America. Deirdre McCloskey has looked at the geographical distribution of Mayan obsidian tools. She notes that, the farther from the sources of their obsidian, the smaller was the ratio of blade weight to cutting length. She comments:

By taking more care with more costly obsidian the blade makers were earning better profits; as they did by taking less care with less costly obsidian.

What we have here, then, is evidence that illiterate, stone age toolmakers were at least as conscious of opportunity cost as any Victorian mill owner, and rather more so than the average socialist planner of the next century. So long, of course, as this is evidence — this is, so long as the tools are distributed as claimed — we have empirical reason for doubting the Polanyi claim that,

previously to our time no economy has ever existed that, even in principle, was controlled by markets…. Gain and profit made on exchange never [before the nineteenth century] played an important part in human economy.

Sean Gabb, “Market Behaviour in the Ancient World: An Overview of the Debate”, 2008-05.