… is from pages 275-276 of Will Durant’s 1939 book, The Life of Greece :
Foreign commerce advances even faster than domestic trade, for the [ancient] Greek states have learned the advantages of an international division of labor, and each specializes in some product; the shieldmaker, for example, no longer goes from city to city at the call of those who need him, but makes his shields in his shop and sends them out to the markets of the classic world. In one century Athens moves from household economy – wherein each household makes nearly all that it needs – to urban economy – wherein each town makes nearly all that it needs – to international economy – wherein each state is dependent upon imports, and must make exports to pay for them….
[I]t is this trade that makes Athens rich, and provides, with the imperial tribute, the sinews of her cultural development. The merchants who accompany their goods to all quarters of the Mediterranean come back with changed perspective, and alert and open minds; they bring new ideas and ways, break down ancient taboos and sloth, and replace the familial conservatism of a rural aristocracy with the individualistic and progressive spirit of a mercantile civilization. Here in Athens East and West meet, and jar each other from their ruts. Old myths lose their grasp on the souls of men, leisure rises, inquiry is supported, science and philosophy grow. Athens became the most intensely alive city of her time.