Theories about the past cannot be scientific, because the past cannot be observed.
The assertion incorrectly assumes that a proposition about x is not scientific unless x itself can be observed in the here and now. In actuality, it is enough for scientists that the truth of the proposition they are investigating would have observable consequences. It is, of course, easy for some thing or process to have observable consequences in the here and now even if the thing or process in question cannot itself be observed in there and now.
Were this not the case, then, for example, the proposition that atoms exist would have been unscientific before the development of electron microscopes, since distinct atoms are too small to observe by less sophisticated means. But the proposition was, of course, scientific even then, because the existence of atoms had observable consequences.
Likewise, scientific theories about the past can have testable consequences. Big Bang theory, for instance, makes a claim about the state of the universe 13.8 billion years in the past. Although no observer could have existed under the conditions posited by the theory, the occurrence of the Big Bang obviously had consequences that can be observed today: the expansion of the universe, the abundance of light elements, and the cosmic background radiation. If we had failed to find any of these predicted consequences, then Big Bang theory would have to have been scrapped or modified. But scientists found what they expected to. The same considerations go for other scientific theories about the past.
Ruse M. 1982. Darwinism Defended: A Guide to the Evolution Controversies. London: Addison-Wesley.
Last updated: 26 Jan 2016
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