For a while no self-respecting report or theory was complete without one.

ECONOMIST: Idea

So the purpose of teaching philosophy was - and remains, in theory - to complete the education of young men and women and permit them to think.

BBC: Why does France insist school pupils master philosophy?

At the moment, this route through the Canadian archipelago is navigable at best for a brief summer spell. (Sovereignty over the passage is one of the Arctic's many unresolved issues: Canada claims it, but the United States says the waters are international.) In theory, a complete opening of the Northwest Passage can shave 2, 500 miles off a journey from Europe to Asia.

ECONOMIST: The Arctic

The black swan theory was developed by Nassim Taleb to describe an event that is a complete surprise, has a major impact, and after the fact is rationalized with the benefit of hindsight.

FORBES: Black Swan Stalking Bernanke Put

In this series, I tell stories of successful business owners who did not complete college, and focused their education on street-smarts in the real world, rather than on academic theory in classrooms.

FORBES: The Education of an Entrepreneur, Episode 2: The Story of Danielle LaPorte