The day in 1492 when Columbus ran into a cluster of islands blocking his way to India is celebrated throughout Latin America and in Spain. It is now fixed in the United States as the second Monday in October, and Americans too have long commemorated the event, both embracing and vilifying the explorer.

Irish and Italian immigrants proudly pointed to Columbus' Roman Catholic religion to fight the prejudice they experienced in their adopted country, and in 1882, they founded the Knights of Columbus, now the world's largest Catholic service organization. But during the late 20th century, Native Americans bristled at the notion of Columbus' "discovery," feeling that their ancestral lands didn't need discovering.

But the real reason Columbus' voyages should be remembered — and celebrated — is for their central role in prying loose European curiosity from the vise put in place by the medieval church.

It took something as dramatic as finding new lands filled with exotic people, plants and animals to liberate Europe's investigative spirit from official opprobrium. Over the two centuries that followed Columbus' initial voyage, robust questioning about the nature of the world turned an inward society outward, fueling an inquisitiveness that would eventually carry Europeans around the world....