Discover, Disbelieve, Disprove, Repeat

A recent email conversation has started me thinking about one of my favorite topics—thinking about data and ideas. It also reminded me that I had been planning to write a post about Karl Popper awhile back and just never got around to it.

I enjoy bringing other disciplines into my thinking about family history and Karl Popper is a good reason to do that. He is famous for at least two reasons. One is the concept of the open society the other is his philosophy of science, specifically his thinking about falsification and that is what my email exchange has brought to mind.

Popper taught that real science is falsifiable and accepting of falsification. As a seventeen-year-old, Popper learned of the new results of a test of General Relativity, Einstein’s theory of gravity. One of the many predictions made by that theory was that light should bend in a gravitational field. Starlight that traveled through a strong enough gravitational field on its way to us should appear to be bent. During the total eclipse of 1919, when the light of the sun was blotted out by the moon, was the perfect opportunity to see if Einstein’s theory of gravitation was right. The measurements were made and the stars closest to the sun during the eclipse clearly appeared to be shifted when compared to where they were expected to be. The sun’s gravity had bent the path of the light. Young Karl was impressed that Newton’s ideas, which had held sway for three centuries, were declared to be false even if they gave incredibly accurate results in most circumstances. It struck him that this was somehow the heart of science, the ability to change ideas once an old idea had been shown to be false.

Later he wrote that only if an idea could be proven false by experiment or observation, was it truly scientific. In a real science, once an idea is proven false, it is abandoned, not held onto for sentimental reasons or stubbornness.

There are lessons here for family historians. We should, of course, try to show our ideas to be true but there is another important way to proceed. A new discovery is immensely exciting but one of the best steps to take after making a discovery is to be a bit skeptical, to disbelieve it. The next thing to do with a discovery is to try to disprove it. That may not feel so exciting but it can be the right way to go. To prove something absolutely true is not necessarily possible but to prove it false can be trivial. Found a recent immigrant in the first census that could include him? Try to find him a decade earlier. He might not be your man after all. Find someone’s baptismal record far from where she lived virtually all of her life? Look for her marriage in that same church. Disprove that the baptism was what you were looking for.

It isn’t always so easy to know when to declare an idea to be false. In the early 1800’s accurate calculations of planetary orbits were made using Newtonian gravitation. The calculated orbit of Uranus, the most distant planet then known, did not match observation well at all. Instead of considering this a falsification of Newton’s theory, a new planet was hypothesized, even farther from the sun and harder to observe. Today, we know that planet as Neptune. It was right where Newton’s equations said it should be. About the same time, problems were found with the calculations of the orbit of the planet Mercury, the closest planet to the sun. A new planet was hypothesized, a planet so close to the sun that it would be nearly impossible to see in the sun’s blinding glare. The hunt was on for this new planet, Vulcan. This time though, it would turn out that the observations pointed to problems with Newton’s equations. Decades later Einstein showed that his theory of gravity made slightly different predictions in the intense gravitational field close to the sun. He calculated Mercury’s observed orbit without adding a new planet. This time, Newton was wrong.

What is the moral of that story? That interpreting evidence in the light of past experience contains some measure of art. It isn’t easy to know when to hypothesize something new in order to save a theory and when a theory has been falsified and a totally new idea is needed. The same man hypothesized both Neptune and Vulcan to solve problems with other planets orbits. Once he was spectacularly right; once it turned out that a totally new way of looking at things was needed.

In the end, some fine ideas turn out to be false. That’s as true in family history as it has been in astronomy. Our tracings of our ancestors’ paths through life rely on us finding the truth, but truth is hard, very hard, to prove. A different strategy is to try to disprove our ideas. We can look in vain for proof that two records correspond to the same person. Proof that they are not the same person can be easy to come by if we look for it. Once we know we are wrong, we can construct the next possibility.

As NASA’s spacecraft fly through the solar system, they are guided by Newton’s equations. Fine though those equations are, they are not quite right.  As accurate as those equations are most of the time, Einstein and Popper both knew that they would never be used for visiting Vulcan.