A Visual Metaphor for Scientific Thinking
November 20th, 2005
I recently came up with a visual metaphor explaining a crucial point about the nature of scientific progress. Many people labor under the delusion that science progresses only by means of proof. That is, we should only believe those statements that have been logically proven by empirical means.
Now, as an advocate of rationalism, I am very much in support of reliance on empirical proof of the propositions we accept. However, few people appreciate that, at the highest level of scientific inquiry, rationalism yields to pattern recognition.
I’m sure that this sounds like some sort of heresy, but consider this: no basic theory in science can be proven. Let’s take the basic theory of evolution. There is no proof -- just lots of evidence that is consistent with the overall theory. To be more specific, we have no proof that homo sapiens descended from some common ancestor of chimpanzees and humans three million years ago -- we weren’t there! There’s no videotape, no direct evidence. It’s all circumstantial. Of course, all that circumstantial evidence is certainly convincing to me. But no scientist can prove that it happened that way.
I’m not arguing that proof is impossible. In the great majority of cases, it is easy to prove the point through empirical observation. The single biggest discriminating feature is historicity. We can readily prove that the speed of light is 3 * 10**8 m/s by simply going into the lab and measuring it. We run into trouble when we try to prove something that happened in the past, such as the Big Bang theory, or any theories of galactic, stellar, planetary, or biological evolution. As soon as you try to make claims about the past, you are immediately in trouble with empiricism because you don’t have the empirical data.
At this point somebody will likely refer to temporal symmetry. We can, for example, retro-predict eclipses of the moon into the past, matching them with historical records. In like fashion, it is possible to work backwards from an existing star’s structure to calculate its previous evolution.
These tricks are possible because we know all the factors and forces at work with great precision. Where such precision is not available, we cannot see backwards into history with any clarity. We are unable to rely on strict empiricism.
At this point I am going to make a suggestion that most scientists will find insulting and heretical. I claim that science makes its highest-level decisions as to accepting or rejecting theories on the basis of pattern recognition, not logic and empiricism. Consider, for example, the contest between the Big Bang and its major competitor, the Steady State theory. During the 1950s, these two theories were neck and neck. But in the 1960s, the discovery of the microwave background radiation started to swing cosmologists towards Big Bang. Note that the background radiation did not prove Big Bang nor did it disprove Steady State -- it was consistent with the Big Bang theory and not consistent with the Steady State theory. Over the years additional evidence arose that lent further support to Big Bang, while no evidence supporting Steady State was found. By 1980, Big Bang was the recognized winner. Yet at no point was Big Bang proven by any logical process. It’s just that the preponderance of evidence seemed to line up in favor of Big Bang.
At this point, I’d like to bash some narrow-minded physicists whom I encountered over at PhysOrg.com. These ignorant fools bashed away at evolutionary psychology, dismissing it as pseudo-science based on what they called "just-so stories". What they don’t realize is that the Big Bang theory is no different: a "just-so story" that just happens to produce results that match up with current observations. Yes, there’s tons of physics involved in the calculations of this particular just-so story. So that makes it a very detailed just-so story -- but it doesn’t change the basic fact that physicists accept a theory that cannot be proven by logic and empiricism.
I hasten to point out that I am not disparaging the Big Bang theory. My point is that every single theory that explains the present through statements about the past is based on "just-so stories". Scientists put the pieces together in the best pattern they can come up with and that becomes their theory. The basic theory of evolution is such a theory. So is evolutionary psychology.
I’d like to close this essay with a visual metaphor showing how it is possible to draw conclusions in evolutionary psychology for which there is no direct evidence. Remember that evolutionary psychology draws on results from a great many fields: anatomy, genetics, anthropology, and so forth. Let’s imagine the contribution of each of these fields as a small part of the overall image of human evolution: