Francis Bacon

At the conclusion of season 3 of the hit TV series Numb3rs, a cop show that also uses math to help catch criminals, spy Taylor Ashby stood on a bridge, looking at Professor Charlie Eppes through connected TV screens. They were in the middle of an intellectual duel, and each time Eppes got a question wrong, Ashby would detonate a bomb. Each time he got a question right, he'd throw away a phone (each phone was used as a detonator.)

Ashby: "Francis Bacon posited four obstructions to the scientific method-"
Eppes: "The idols of the mind." A phone is tossed. "The cave." Another phone. "The theatre." Another phone. "The tribe." Once more. "And..." Ashby dials. "Umm..."
Ashby detonates a bomb.
Eppes: "THE MARKETPLACE! Damn... Dammit! You didn't give me enough time!"
Ashby: "I'm not just testing your mind! I'm testing your heart."

That was the first time I'd ever heard of Francis Bacon or his idols of the mind (that's an awesome show by the way, you should check it out.)

In any case, we have four idols of the mind. The cave is where people get stuck in their own area, unable to reach out and look at other areas of learning. Historians stick to history, mathematicians to math, etc. They never look outside the box.

The theatre is where people look to fiction and use that as knowledge. By reading fiction novels, watching fiction movies or plays, they take it as real and use it as true knowledge when it obviously isn't.

The tribe is human errors. Things such as exaggeration, prejudices, and other common tendencies that hinder our learning. By exaggerating or prejudicing, or any other common mistake we confuse others and slow learning.

The marketplace is when words replace thoughts. People think they win an argument because their words sound better and the other person has nothing to come back with, but they have better thoughts. We use words to communicate our thoughts, and it's the thought that matters, according to Bacon.