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No. 910:
El Cid and Aristotle

Today, a city falls. And the seeds of the scientific method are sown. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

Do you remember Charlton Heston playing the Spanish hero El Cid -- freeing the city of Toledo from Moslem rule in AD 1085? Never mind that the real El Cid was in fact a murdering, looting barbarian. Never mind that he wasn't even around when Toledo fell. Actually, Toledo's Moslem ruler opened the gates to the Christians so he could escape from enemies inside the city.

Still, this was one of the great moments in Western intellectual history. When they got to the library, Christian scholars learned how far they'd fallen behind the Moslems.

For four centuries Arab scholars had been the chief preservers of the ancient Greek books. Plato and Aristotle had become distorted echoes in the Christian world. Now Europeans saw their legacy first hand, and they were stunned by its brilliance.

James Burke tells how the Arab and Jewish scholars of Toledo graciously led academic tourists from the North through their trove of literature. Those visitors felt like primitive savages among the mountains of newly discovered books.

The works of Aristotle presented them with a kit of logical tools that opened a stunning array of capabilities. They rediscovered the syllogism -- that miraculous means for using two facts to generate a third. For example:

Skin gets wet with perspiration.
Moisture escapes from things through holes.
Therefore, skin must have small holes in it.
We've suddenly generated a third fact, seemingly out of thin air.

The French scholar Pierre Abelard seized on the new logic. He turned Aristotelian dialectic loose on Holy Scripture. "By doubting we come to inquiry," he said, and "by inquiring we perceive the truth." And that, Burke reminds us, was revolution. Abelard wrote four rules for inquiry:

Use systematic doubt and question everything.
Learn the difference between rational proof and persuasion.
Be precise in use of words, and expect precision from others.
Watch for error, even in Holy Scripture.

It would be five centuries before science would fully embrace this old logic in its new wrapper. For the moment, theologians tried to ride the shock waves Abelard had unleashed.

Medieval lawyers were first to arm themselves with these new tools. By the mid-13th century the Church finally acknowledged Aristotle. When they did, Thomas Aquinas moved in and built a theology based on Aristotelian logic.

Out of that came a new theological statement: No longer "understanding can come only through belief," but rather, "belief can come only through understanding." And there, of course, was modern science -- in its purest embryonic state.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)

Burke, J., The Day the Universe Changed, Boston: Little, Brown and Company, 1985, Chapter 2, "In the Light of the Above."