Logical thought and beliefs

People have lots of arguments (at least I do) about politics and human affairs.  In most cases we have no chance of persuading anyone, as we don’t form beliefs based on logical thought.

“Beliefs” are for religion.  In logical thought we call them axioms. However, in most arguments we don’t question our axioms and believe the conclusions, however shaky the line of reasoning.  It would be nice to see decisions made on the basis of evidence, but too often the decision is made based on prejudice and the reasoning tailored to the conclusion.  No group is immune (although some may be more prone to it than others).

I find it helpful to ask myself “what evidence would cause me to change my mind about a subject?”.  If I know what to look for then I can question my conclusions independently of the “reasoning” that created them.

Take Global Warming – as an example.

We have all sorts of reasons for concluding that greenhouse gases cause heat retention in the atmosphere, and that if there were no greenhouse gases the earth would be many degrees cooler.  There are a few hidden axioms there, but it can be taken as near to a “fact” as science gives.

The global climate record is showing warming based on temperature gauges and proxy measurements.  It is therefore logical to conclude that greenhouse gases are causing the current warming.  Alternatively we have to show both:

  1. why greenhouse gases are not warming the planet?
  2. what is causing the warming instead?

All that remains is to measure the coefficient of warming.  From that we can predict how much warming to expect in the future given that we keep treating the atmosphere like a sewer.

Not so fast!

The scientific method goes: evidence, theory, prediction, measurement (rinse and repeat).  So far we have shown the first 3, how have predictions made in the previous decades matched reality?  The answer is well enough (within the uncertainties that come with climate models) but not conclusive enough to be considered “scientific fact”.

So if not “scientific fact” then what?  We make all sorts of public policy on evidence that is much weaker than the evidence for global warming.  (just look at economics, which is little better than guesswork).  We might think of the difference between criminal vs civil law.  In criminal law we are looking for “beyond reasonable doubt” (yet we use evidence which is much weaker than the evidence for global warming).  In civil law we have to allow a decision on balance of probabilities.  In public policy we have to balance the costs and risks of BAU vs the costs of action. Physics doesn’t say anything about the costs (that is economics) but please use the best available physics to make your estimates.

So what would make me doubt global warming?

  • I could question the axioms:  Do greenhouse gases really cause warming of the atmosphere?
  • I could question the measured temperature record
  • I could question the proxy temperature record
  • I could question the predictions of the climate models
  • I could find real evidence of another mechanism causing heating the atmosphere

It turns out in this case the first bullet point is crucial, so long as at least one of the others stands.  So if you want to convince me that global warming is bogus, show me real evidence that the physics is wrong!

If you are convinced that human activity is not warming the planet, then I challenge you to consider what evidence would make you change your mind.