1500s: Renaissance thinkers, like Machiavelli, emphasize logic and rational pragmatism over religious ethics in political analysis

Today: Political campaigns are driven more and more by advertising and market research. This allows candidates to support only popular positions, often to the chagrin of voters who doubt the morality and ethics of political candidates.

1534: Giulio de Medici becomes the first in a long succession of Italian popes.

Today: Elected in 1978, Pope John Paul II remains the preeminent Roman Catholic leader. He was the first Polish priest to be chosen for the position, ending an uninterrupted line of Italian popes.

1513: Polish astronomer Nicolaus Copernicus begins writing his major work, De Revolutwn-ibus Orbium Coelestium Published after his death in 1543, it proposes that planets revolve around the sun.

1633: Italian astronomer Galileo Galilei supports Copernicus' theories As a result, he is jailed because the Roman Catholic Church teaches that Earth...