In This Idea Must Die, cosmologist Sean Carroll argues that the criterion of falsifiability as a characteristic of scientific theories must die because it is holding back the advance of science. So what is “falsifiability” and why does it matter?
First of all, falsifiability is not a scientific theory at all. It is a philosophical proposition about the nature of scientific theories. Basically it is the tent pole for Karl Popper’s attempt to distinguish science from other things like pseudo-science, metaphysics, and mathematics. It states that unless a theory allows for the possibility that certain observations would prove the theory false, the theory is not a scientific one.
Karl Popper (1902–1994) in his seminal treatise, The Logic of Scientific Discovery, explains his stand as:
Natural laws might be compared to ‘proscriptions’ or ‘prohibitions’. They do not assert that something exists; they deny it. They insist on the non-existence of certain things or state of affairs, proscribing or prohibiting, and ruling them out. And it is precisely because they do this that they are falsifiable. If we accept as true one singular statement which infringes the prohibition by asserting the existence of a thing (or the occurrence of an event) ruled out by the law, then the law is refuted.
Strictly existential statements, by contrast, cannot be falsified. No statement of an observed event can contradict the existential statement, ‘There are white ravens’. Only a universal statement could do this. On the basis of the criterion of demarcation here adopted I shall therefore have to treat strictly existential statements as non-empirical or ‘metaphysical’. —The Logic of Scientific Discovery, p. 69
Thus we see that the statement “There exists a multiverse” is necessarily existential and thus metaphysical.
But if we say, “Because the multiverse does not exist, I therefore know that there are not an infinite number of copies of me,” we have made a falsifiable statement. Anyone could easily falsify that statement by producing evidence of there being an infinite number of copies of me. In fact, even one perfect copy of me (identical down to the very last atom and identical in all life experiences down to the finest detail) would falsify the statement. Thus the negation, “There is not a multiverse,” is valid as scientific theory.
The desire to eliminate falsifiability as a criterion of demarcation is simply a way to allow certain favored wild, non-scientific ideas to sneak in as science and thereby gain the prestige that our society accords to science.
It’s important to note that pseudo-science which we all view with contempt gets lumped in with mathematics, which we all respect. So there is meaning and importance on both sides of the divide between science and non science. Moreover sometimes metaphysical theories like the atomic theory of the ancient Greeks can migrate from metaphysics to science as more refined techniques of observation are developed. In fact, it’s even possible for pseudo-science to enter the fold of science as happened with the theory of plate tectonics which the scientific community of 1912 dismissed as preposterous but which is now accepted as obvious.
When it comes to the multiverse the situation is clear. Multiverse theory cannot be falsified. It cannot be observed at all. It exists only as a mental speculation (or as Popper puts it, “an existential statement). It is therefore not science. Multiverse theory is metaphysics. Or, if you prefer, it is pseudo science. But science it is not. Popper’s rule for demarcation makes it easy to so classify multiverse claims.
The desire to eliminate falsifiability as a criterion of demarcation is simply a way to allow certain favored wild, non-scientific ideas to sneak in as science and thereby gain the prestige that our society accords to science. But if we grant scientific status to the multiverse by eliminating falsifiability as a criterion of science, we must also grant scientific status to astrology which has a long history of not being falsifiable. (And by the way, Kepler happened to be a first class astrologer which skill he used to help support himself while he worked on his studies of the orbits of the planets.)
It is important to remember that it does not matter whether falsification is possible on a practical level. It may well be impossible to test the theory by any means available to technology. What matters is that the theory is so stated that some sort of test is theoretically possible.
I will close with this quote which summarizes Popper’s views rather well:
Falsificationists…believe…that we can never give positive reasons which justify the belief that a theory is true…We hold that…the rationality of science lies not in its habit of appealing to empirical evidence in support of its dogmas—astrologers do so too—but solely in the critical approach— in an attitude which, of course, involves the critical use, among other arguments , of empirical evidence (especially in refutations)….therefore, science has nothing to do with the quest for certainty or probability or reliability…we are only interested in criticizing [theories] and testing them, in the hope of finding out where we are mistaken; of learning from our mistakes; and, if we are lucky, of proceeding to better theories. —Conjectures and Refutations, p. 228
See also: Will there still be science in 2020?
and How the multiverse was created
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