Usury

I just finished a fascinating book of essays by Jacques Le Goff called Time, Work,&Culture in the Middle Ages that raised some questions for me about the medieval position on usury. As anyone knows who's read Merchant of Venice, the practice of charging interest was forbidden to Christians during the Middle Ages, and was one of the principal causes of animosity towards the Jews. (Who were allowed to lend money at interest to non-Jews.) Le Goff traces the change in attitude towards interest and relates it to the development of the mechanical clock.

It was Lewis Mumford who first wrote about the importance of the mechanical clock in Technics and Civilization. Originally conceived as a more efficient means of keeping the hours for prayer, the standardization of time allowed for time to be represented as a commodity which could be recorded, bought, and sold--basically making way for the modern theories of labor according to an 8 hour day. (Clearly the ideas about musician labor are pre-modern.)

Le Goff contends that the scholastic argument broke down with the invention of the mechanical clock. It had been argued that interest was unlawful because it represented the purchase of time on capital, and time belonged to God alone, and therefore could not be put to sale. With some casuistic justifications for the merchant's hazard (the lucrum cessans, periculum sortis, and ratio incertitudinis--the tying up of cash in long term undertakings, perils of fate, and uncertainty of success) arguments began to be made in favor of an interest-based economy.

There are also some interesting thoughts by Le Goff on the contrast between Jewish, Pagan, and Christian views of the nature of time, but I won't detail those here. My question for anyone who has stayed interested through the first three paragraphs is this: Do the scriptural prohibitions against lending or borrowing at interest ever concern you? How do you square them against the success of the modern economy? Are you aware of anyone who writes on the subject? I'd appreciate any thoughts...