Since a tariff on imports played little part in Greek life, except in so far as it was imposed for sumptuary or war purposes,208 the perplexing modern problem of the protective tariff scarcely came within the horizon of Greek thinkers. Plato would prohibit the import of certain luxuries, as a moral safeguard. He divides merchandise into primary and secondary products, and would not permit the import of the latter.209 Elsewhere, however, he legislates against imposts upon either imports or exports, though unconscious of the significance of his suggestion.210
He appreciated something of the function of exchange in society. It performed a very important service, as a mediator between producer and consumer.211 Like money, it served to equalize values, and thus acted as an aid to the satisfaction of needs.212 When limited to this primary function, it was of advantage to both parties to the exchange,213 and merchants and retailers had then a real part in the production of values.214
The sweeping assertion is too often made that the Greek people were hostile to trade, and therefore that their theorists were especially opposed to it. We have already seen how false this idea is for the Greeks themselves,215 but it also needs a great deal of qualification in the case of their writers. Their hostility is directed especially against the more petty business of retail trade (καπηλική) rather than against the extensive operations of the merchant (ἔμπορος). But their opposition even to this is not entirely undiscriminating. We have seen that Plato clearly understands the necessity of exchange to the life of the state.216 He admits that even retail trade is not necessarily evil.217 The chief reason why it appears so is because it gives free opportunity for the vulgar greed of unlimited gain, which is innate in man.218 If the noblest citizens, who are governed by rational interests, should become retailers and innkeepers, the business would soon be held in honor.219