Tuesday, 24 May 2016

Truth Engineering

I have a lot of confidence in bridges. That's not a gut reaction, but an empirical assessment. As a child I would get very nervous every time I crossed nearly any kind of bridge. Today that nervousness has gone. That's not because I grew up and stopped worrying, it's because at the age of five or six I independently created one of the major techniques of Cognitive Behavioural Therapy and used it to beat my nervousness into submission. Every time I cross a bridge, before the nervousness can even take hold, the rational-brain preempts it with a "And what is the likelihood that this bridge collapses this time we cross it?"

Bridges don't tend to collapse when you cross them because people are pretty good at building bridges. When bridges do collapse it is usually because no one is listening to engineers who say things like, "You really have to do maintenance on bridges or they eventually fall down."

Of course bridges sometimes do collapse in spectacular ways:



In 1940 the Tacoma Narrows bridge shook itself to pieces spectacularly. It waved like a flag in the wind and fell apart. I saw a video of this in grade nine or ten science as an example of the incredible effects of resonance. So if I had been crossing that bridge in 1940 and it began to flap in the wind and fall apart, I might rightly say, "Maybe bridges aren't so safe. Maybe engineers don't know what they are doing."

Well, engineers don't know what they are doing, but they know they don't know what they are doing, and they do their best to know what they are doing to the extent possible. They don't want bridges to collapse in strong winds so they build models of bridges and subject the models to strong winds. That isn't a sure thing for prevent bridge collapses, but it may well have prevented another Tacoma Narrows.

Engineering takes the reality that we want a stable bridge, and finds the mathematics, physics, materials and tests that allow us to build that.

Logic is truth engineering. The reality is that we want to be able to tell a well supported conclusion from a poorly supported one - something we ought to believe from something we ought to dismiss. The tools we use to address it are abstract reasoning and... well... that's all, just abstract reasoning. The result is that logic - classical logic at least, that is, the kind of logic that anyone outside a university program in philosophy or mathematics calls "logic" - is dismal, failed truth engineering. If logic built bridges then I would never set foot on a single one of them.

I want to be clear about which was this relationship runs. If you believe that logic is the underlying stuff of the universe then you basically believe the farthest thing from the truth possible - which isn't surprising since you apparently have confidence in logic. The hypothetical syllogism from classical logic isn't the basis for my knowing that "if logic works then there is no such thing as a married bachelor" plus "logic works" leads to "there is no such thing as a married bachelor". No, I know that the last statement followed from the first two because that is the meaning of the words "if" and "then". The hypothetical syllogism is a model of that concept put into a formal system in the same way that the blueprints for a bridge only model the bridge - you can't cross the canyon on them.

So when someone brings up a logical fallacy they are saying that within the model of determining truth and validity of statements the kind of reasoning being used isn't relevant. In fact, they are often saying that the kind of reasoning being used simply isn't modeled. If Joe Smith makes a very compelling and seemingly irrefutable case that we ought to back him in his investment scheme, then me pointing out that Joe Smith is a known con artists who has been repeatedly tried and sentenced for fraud is what is called an Ad Hominem. Smith's argument stands on it's own, regardless of the character of Smith.

This, like the flailing bridge, ought to be a warning signal to us: the symbolic system we are relying on to determine the validity of statements is badly broken. "I can't find a problem with his reasoning, but given that he has swindled lots of people out of a lot of money in the past, I'm not inclined to believe him anyway" is a perfectly good argument. It's a fine formulation.

None of this would come as a surprise to anyone who studies logic beyond a first year critical thinking course or an internet list of logical fallacies. The defects of classical logic are many and well discussed. Alternate systems have been created and debated for a long time. But the basic idea of ORs and ANDs and IFs doing what they do and of the irrelevance of non-abstract entries into logic persists all over the lay-understanding of logic.

Engineering must appeal to the real world. Truth engineering that doesn't appeal to scientific experiment is useless because it ignores our current working method of telling fact from speculation. Truth engineering that doesn't appeal to psychology or at least neurology is useless because it doesn't make any reference to the methodology that physically underlies our determinations of truth.

Cognitive biases have their own problems, but they are a far superior model to logical fallacies if you want to do a better job at getting at the truth. Instead of thinking "Ad Hominem is a fallacy" think, "People, including me, have a tendency to believe that people they like are correct and people they don't like are incorrect but that is at best a very weak measure and I should be careful not to overvalue it." Stopping to wonder why you find something convincing as a check against its validity is a much better defense than trying to determine in some absolute sense whether or not the thing is convincing. The former encourages you to spot your biases, the latter discourages it.

So add logic to the list of things that I think are stupid, along with free speech and presumption of innocence. It's going to be a long list.

No comments:

Post a Comment