Tuesday, March 24, 2015

The danger of weak arguments

Weak arguments are not neutral, they are damaging for technical or scientific propositions.

There's overwhelming evidence for the proposition "Earth is much older than 6000 years." (It's about 4.54 billion years old, give or take fifty million.) Let's say that Bob, who likes science, as long has he doesn't have to learn any, is arguing with Alex, an open-minded young-Earth creationist:

Alex: Earth was created precisely on Saturday, October 22, 4004 B.C., at 6:00 PM, Greenwich Mean Time, no daylight savings.

Bob: That's ridiculous, we know from Science(TM) that the Earth is much older than that.

Alex: What science? I'm willing to listen, but not without details.

Bob: Well, scientists know exactly and it was in Popular Science the other day, too.

Alex: What did the Popular Science article say?

Bob: I forget, but it had two pretty diagrams, lots of numbers, and a photo of Neil DeGrasse Tyson in his office. He has a wood model of Saturn that he made when he was a kid.

Alex: So you don't really know how the age of the Earth is calculated by these scientists, you're just repeating the conclusion of an argument that you didn't follow. Maybe you didn't follow because it's a flawed argument.

Bob: I don't remember, it's very technical, but the scientists know and that's all I need. Why don't you believe in Science(TM)?

Alex: It appears to me that your argument is simply intimidation: basically "if you don't agree with me, I'll tag you with a fashionable insult." Perhaps that's also the argument of the scientists. They certainly sound smug on television, as if they're too good to explain themselves to us proles.

Alex, despite his nonsensical belief about the age of the Earth, is actually right about the form of argument; by presenting a weak argument for a truthful proposition, Bob weakens the case for that proposition. Note that this is purely a psychological or Public Relations issue. Logically, a bad argument for a proposition shouldn't change the truth of that proposition. Too bad people's brains aren't logical inference machines.

(There's a Bayesian argument for downgrading a belief in a proposition when the case presented for that proposition is weak, but a rational person trying to learn in a Bayesian manner the truth of a proposition will do a systematic search over the space of arguments, not just process arguments collected by convenience sampling.)

This is one of the major problems with people who like science but don't learn any: because of the way normal people process arguments and evidence, having many Bobs around helps the case of the Alexes.

A weak argument for a true proposition weakens the public's acceptance of that proposition. People who like science without learning any are fountains of weak arguments.

Let's convince people who "like science" that they should really learn some.