Tuesday, March 26, 2013

Texas Sharpshooter: Adventures in Logic III

Dear Children:

This may be new to you, but bear with me. You will be rewarded.

Correlation does not imply causation (cum hoc propter hoc). That is Latin for "with this, because of this". It is a term used in science and statistics to emphasize that a correlation between two variables does not necessarily imply that one causes the other. Many statistical tests calculate correlation between variables. A few go further and calculate the likelihood of a true causal relationship.

The opposite assumption, that correlation proves causation, is one of several logical fallacies by which two events that occur together are taken to have a cause-and-effect relationship. This fallacy is also known as cum hoc ergo propter hoc, Latin for "with this, therefore because of this", and "false cause". A similar fallacy, that an event that follows another was necessarily a consequence of the first event, is sometimes described as post hoc ergo propter hoc (Latin for "after this, therefore because of this").

You only have to remember the gist: one thing does not cause the other because they occur near, before or after the other thing.

One interesting version of this is in the news every day; the medical news. It’s called The Texas Sharpshooter fallacy. Sorry, there is no Latin word for Texas.

This fallacy posits that if there are at least two factors that present themselves in a large sampling of data, the same conclusion may be drawn as from the whole sample. It’s as if someone shot a million .45 rounds in the broad side of a barn. After examination of the bullet holes, our gunman draws a target around two of them claiming a medal for marksmanship.

It would be funny if it didn’t have tragic consequences. Our brains are wired to look for patterns. That’s how we recognize faces for instance.

Thousands of parents have refused to have their children vaccinated because of this cruel fallacy. A child has autism, that child got vaccinated; vaccination causes autism. It’s not as if parents were making a tragic mistake for their own children but they are also risking exposure to Rubella, for instance, to their children’s classmates. Remind me to talk about Moral Hazard some day.

Not that there aren’t hilarious examples of this as well, Sports radio is full of it. Some talking head notices that Bruiser’s ERA seems to fluctuate with his picture on the first page of the sports section of the paper. That’s fun but no less a load of equines puckes.

I’m just sayin’


Monday, March 25, 2013

So’s Your Old Man: Adventures in Logic II

Dear Children:

In the study of logic, there is a fallacy called argumentum ad hominem (against the person). Of course it is often a personal attack but more often it is an attack made against an adversary’s associations, lifestyle, education and parentage. It is a fallacy because such an attack does not speak to the validity of a proposition. Girls aren’t supposed to know anything about math or science. Short people don’t know basketball. Plain people should not be giving fashion tips. Beware of Greeks bearing gifts. You get the idea.

There are many specific brands of the ad hominem fallacy such as Circumstantial when a claim is made by someone who has special or secret knowledge. When someone says they have secret knowledge, that claim may be true or false but the speaker’s credibility is nonexistent.

A proposition may be attacked when the source appears to have a Conflict of Interest. For a source to be authoritative it must be both objective and impartial. The evidentiary weight of an argument diminishes with the benefit that accrues to the source.

Guilt by association is also a fallacy in this category. There is no bearing on the validity of a statement concerning crime from the mouth of a criminal.

But, it’s another special kind of ad hominem fallacy we see around us the most. It is called Tu Quoque; literally “you too”. This, finally, is a subject dear to the hearts of us all; hypocrisy.

We are highly sensitive when it comes to hypocrisy. “Do what I say, not what I do.” We don’t listen to those who fail to practice what they preach. We know for sure that “If you lie down with dogs, you get up with fleas” attributed to Benjamin Franklin’s Poor Richard’s Almanac. In modern political parlance, we call such people flip-floppers or worse. You are sensible to be suspicious of such people. Unfortunately, your suspicion does not amount to a refutation of their claim.

Please understand that it must be this way. No less a figure than Jesus has asked us to examine our hearts to see if we are righteous enough to cast the first stone (John 8:7). In logic, too, the sins of a speaker do not say a true thing about the speaker’s words.

If a speaker is wrong, we’ll just have to prove it another way.

I’m just sayin’


Sunday, March 24, 2013

Straw Man: Adventures in Logic

Dear Children:

Recognizing specious argument isn’t easy. Moreover, we often know something is wrong but we have no name for it. This begins a series about the various ways arguments are distorted.

Now don’t get me wrong. Some things aren’t open to examination by logic. Take matters of faith for instance. If you say you believe in Unicorns you have expressed a belief. No one can tell you that you don’t believe in Unicorns. Nowhere in all the rhetorical arts is it possible to fully know another person’s mind.

And, there are other statements of fact that do not have to be proved-up logically in order to be true. You say it is in the paper today that Bruiser hit two home runs. Such a statement is likely to be true.

It’s the statements that are offered up as reasoned and true that I want to discuss here. In these cases, statements used to argue a particular position are always subject to the crucible of logic.

One of my favorites is called Straw Man. It is a fallacy one finds everywhere. But first, let’s understand a principle of logic called argumentum ad logicum (argument to logic). A proposition is not false because the logic used to prove it is invalid. In other words, we cannot say that something is false and base it on the notion that the proposition was not proved with impeccable logic. That’s just fair. Understand that a statement may be valid even though it was wrongly argued.

That's right.  We are in the business of arguing such points rightly so that we can make a judgment about validity.

That’s where Straw Man comes in. Straw Man is a particular version of argumentum ad logicum that refutes an extreme version of someone else’s argument rather than the actual argument he or she has made. For instance, if some outrageous description of the other’s statement is false, what he actually said must also be false. Politics is rife with this fallacy.

Senator Snort: This fighter jet strikes me as frightfully expensive.

Senator Blather: Senator Snort is such a penny-pincher. He would leave our country defenseless.

Do you see? Senator Blather has fashioned a cartoon version of what Senator Snort had to say. Then, because penny pinchers and those weak on defense are silly, we needn’t listen to him. In no way did Senator Blather actually engage Senator Snort’s statement.

Here’s another one: “We know that evolution is false because we did not evolve from monkeys”. Never mind that evolution does not aver that humans evolved from monkeys. That’s a straw man. Make up something false to knock over and, in so doing, belittle someone who wants to engage on a serious topic.

With a little practice you will recognize this fallacy in everyday life. See if this one is familiar:

Mom: Today we’ll clean out the closets. They are looking messy.

Kid: We cleaned out the closets last Easter. Must we clean them every day?

Mom: Who said anything about every day? You just want to keep your crap forever. That’s ridiculous.

There are two straw men in one short argument. The important thing to note here is that nothing was accomplished.

I’m just sayin’