Saturday, 24 September 2005

Prove me Wrong!

One of the most fundamental features of a truly scientific theory is that it must be falsifiable in principle. By falsifiability I mean the characteristic of a theory that enables it to be tested by means of experimentation. A theory that cannot be falsified by an experiment is just metaphysical or philosophical. It is beyond the scope of science. For example, if I say that people only die when the time comes, it cannot be disproved in principle. That is because there is no experiment or situation where this theory can be shown to be wrong: if someone dies, the time arrived, if doesn´t, the time hasn´t arrived.

When you find someone defending a theory by defying you to prove that the theory is wrong and saying that if the theory cannot be proved wrong it must be right, be sure that the person is not a scientist or is a bad scientist. Theories that cannot be proved wrong are not good, they´re useless. A theory that cannot be falsified has no predictive power, i.e., you cannot predict the outcome of new experiments, cause if you could, the theory could be tested just by doing that particular experiment and verifying if the result is the same as the prediction. The more predictions of a theory are confirmed, the more the theory is trusted, but rigorously you can never say that a theory is completely correct. I´ll post something later showing how this relates to Bayesian inference.

It seems too simple, but this simple requisite is the main reason why a god cannot enter in science. That´s because gods cannot be falsified in principle. There is no experiment or situation that prove that they don´t exist. The same way, any theory that include gods are not scientific too (e.g., intelligent design).

So, adding to the items you must check to judge a theory, try to find a way to test it. If it cannot be tested in principle, if the theory cannot make a prediction but just fit the already known experiments, be very suspicious of it: probably it is not worth the time you will spend trying to understand it.

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