On critical thinking

Originally posted as a comment to my friend Scott's blog, over here, but I think it stands well enough alone for me to post it here:

I think one of the major problems in all intellectual discourse (or lack-of-intellect-ual discourse) is that critical thinking is a skill not sufficiently well taught. At the risk of sounding arrogant, I tend to think of myself as a reasonably intelligent person; further braving the danger of the impression of nationalistic pride, I think that I have come through a respectable educational path: Swedish elementary and secondary schools, Canadian universities. Even so, and even given a natural tendency toward skepticism and a love of learning, I didn't learn to critically disseminate sources until rather recently; presumably it was gradual over the course of many years, but it reached a culmination (relative, of course, to whatever my present understanding may be considered to be) less than two years ago when I started to read research papers and came to realise that even at the cutting edge of scientific endeavours, there are opinions and errors and uncertainty, and even in very well-written papers by very intelligent and educated people, even in papers with terrific and accurate ideas, there may be errors. (Reading Darwin's The Origin of Species was perhaps a more obvious lesson in the same, although more recent.)

So where am I going with this? Well: Even with the resources available to me, I was still left with some nasty residual notion that purported factual writings fell into the two categories of true and not true. This is, alas, a dogmatic view—one with room to eliminate dogma I could identify as false, happily, but dogmatic nonetheless. Here we go back to Arrogance Land: I suspect that if I was left with so faulty a perception for so long, then a great many people—certainly not all! But a significant chunk of the population, whether large minority or majority great or small—are probably likewise impaired. Evidence certainly seems to back up my arrogance, here.

Now, I think it is essential for a rational view of the world to accept or reject every purported fact provisionally, and to keep in mind that even well-established facts like the theories of gravity, electromagnetism, and evolution have a probability of (very very slightly) less than 1, and even way-out-there conjectures like (equivalently) Christian theism, voodoo, and Russellian teapotism (with apologies to the late, great Russell for coining such a term) a probability (very slightly indeed!) higher than 0. P = 1 is dogmatic acceptance. P = 0 is dogmatic rejection. 0 < P < 1 is acceptable territory for rational thought. (Of course, we may often have ε ≈ 10^-x for quite a large x…)

As I'm writing that, it seems to me that a reasonable hypothetical model for Truth would be a Bayesian network of facts…