Today’s post is part of a special series here on Planet Pailly called Sciency Words. Every Friday, we take a look at a new and interesting scientific word to help us all expand our scientific vocabularies together. Today’s word is:
UNDERDETERMINATION
This word comes to us not from science itself but from the philosophy of science. According to the philosophy of science, when we have two competing theories to explain some natural phenomenon, we are supposed to choose which theory is correct based on the evidence available to us. But what happens when we don’t have enough evidence?
For example, let’s say that I theorize that horses are slow moving animals that can only trot, and you theorize that they are capable of running really fast. If the only experience either of us has ever had with horses is watching one stand still eating its hay, then our two theories are underdetermined by our lack of experience with horses.
In the recent evolution vs. creationism debate between Bill Nye the Science Guy and Ken Ham of Answers in Genesis, Ken Ham never used the word “underdetermined,” but that is exactly what he was trying to argue: that our choice between evolution and creationism is underdetermined by a lack of evidence. Of course, that’s not the case at all. There is an overwhelming amount of evidence in support of evolution and plenty of evidence to refute creationism as well.
One example of genuine underdetermination is in the search for life on Mars, where there are some signs of the possibility of life, some evidence that makes life less likely (but still not impossible), and as of yet no discovery of an actual Martian organism, living or dead. Another example of underdetermination are the various competing versions of string theory, which as I understand it remain untested and untestable due to the limits of technology.
Underdetermination is always a temporary problem. It would not take long to prove which of our theories concerning horses is correct. We’d only have to go to a farm or perhaps a rodeo, or we could simply look up horse videos on YouTube. As NASA rovers continue exploring Mars, the question of Martian life will be resolved. As for string theory, I’m sure the necessary technology will be invented eventually. Of course if some people refuse to accept any evidence that disproves their preferred theory, that is another problem entirely, and the sciency word for that is confirmation bias.
Planet Pailly 
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