What is Meant by "Scientific Evidence" for Common Descent?
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Scientific theories are validated by empirical testing against physical observations. Theories are not judged simply by their logical compatibility with the available data. Independent empirical testability is the hallmark of science—
in science, an explanation must not only be compatible with the observed data, it must also be testable. By "testable" we mean that the hypothesis makes predictions about what observable evidence would be consistent and what would be incompatible with the hypothesis. Simple compatibility, in itself, is insufficient as scientific evidence, because all physical observations are consistent with an infinite number of unscientific conjectures. Furthermore, a scientific explanation must make risky predictions— the predictions should be necessary if the theory is correct, and few other theories should make the same necessary predictions.
As a clear example of an untestable, unscientific, hypothesis that is perfectly consistent with empirical observations, consider solipsism. The so-called hypothesis of solipsism holds that all of reality is the product of your mind. What experiments could be performed, what observations could be made, that could demonstrate that solipsism is wrong? Even though it is logically consistent with the data, solipsism cannot be tested by independent researchers. Any and all evidence is consistent with solipsism. Solipsism is unscientific precisely because no possible evidence could stand in contradiction to its predictions. For those interested, a brief explication of the
scientific method and scientific philosophy has been included, such as what is meant by "scientific evidence", "falsification", and "testability".
