Is evolution scientific fact or just a theory?
According to the opinion promulgated by some opponents of the theory of evolution, scientific facts should be taught at schools and not unverified theories.
To begin with, it should be pointed out that this opinion is not generally held. A non-negligible part of the public thinks that, rather than teaching actual facts, schools should teach students how to discover these facts and how to deal with them. Acquainting pupils and students with unverified theories is very useful for acquiring and developing these skills and may even be essential. In actual fact, this book refers to some more “exotic” theories and hypotheses for just this reason.
Secondarily, this objection is proof of the person’s lack of knowledge or failure to understand the basic principles of general scientific methodology. Every theory or hypothesis actually represents a model of a certain phenomenon (process) and thus our idea of why and how a certain phenomenon occurs. The only way to verify whether our model is the correct one is to verify the truth of all the consequences following from the potential validity of our model. Consequences following from the model can have the nature of a statement with a general quantifier (It holds for all X that Y, for example, “All organisms on the Earth use a universal genetic code”) or a statement with an existential quantifier (There exists at least one X for which it holds that Y, for example “An animal exists that is capable of obtaining all the necessary organic carbon by photosynthesis."). Empirically, i.e., for example experimentally, it is possible to confirm the validity of statements with an existential quantifier by actually finding some X for which it holds that Y. However, these statements cannot be empirically proven to be untrue as we can never be sure that we have examined all possible X. In contrast, statements with a general quantifier can only be shown to be untrue empirically in that we find at least one X for which Y is not true; however, the validity of a statement with a general quantifier can never be confirmed, because once again we can never be sure that we have examined all X. However, the meta-statement mentioned at the beginning of this section, “All the consequences following from the potential validity of our model are true.” has the nature of a statement with a general quantifier and thus, in the optimum case, we can overturn it but never prove it.
The philosopher Karl Raimund Popper (1902–1994) was apparently the first to quite convincingly demonstrate that it is not possible to prove, i.e. verify, any scientific theory. It is only possible to attempt to overturn it, i.e. falsify it. If a theory is capable of resisting sufficiently intense attempts to overturn it for a sufficient length of time, it can be considered to be relatively verified and thus conditionally valid. However, no theory can be considered to be definitively confirmed; it is always necessary to bear in mind the possibility that even the best-confirmed theory may be erroneous. The requirement that only scientific facts be taught and never unverified theories is thus not practicable unless, of course, we don’t want to limit ourselves to teaching some parts of mathematics.