Against Karl Popper

I've always liked Popper's answer, but hear them out. First, what is the answer?

Popper was struck by Einstein’s prediction. “Now the impressive thing about this case,” he wrote decades later, “is the risk involved in a prediction of this kind.” Had the measurements found Einstein in error, Popper said, the physicist would have been forced to abandon his theory. Popper built his demarcation criterion around the bravado of wagering against refutation: “One can sum up all this by saying that the criterion of the scientific status of a theory is its falsifiability, or refutability, or testability.”

Second, what was the answer meant to contrast?

All demarcation criteria are designed to exclude something. What Popper really wanted to do was to show why psychoanalysis and Marxism were not scientific. Those theories had been widely understood as “scientific” in his Viennese milieu because of a logical empiricist theory called verificationism. According to this view, a theory is scientific if it is verified by empirical data.

From my perspective, successfully excluding Marxism and psychoanalysis from science justifies the project. However, others have disagreed, and not only Marxists and psychoanalysts. 

First, it is difficult to determine whether you have actually falsified a theory....  Not so fast. How do you know that your experimental result was accurate?

That's a terrible objection. Falsification is about whether or not the theory could in principle be falsified. The fact that it may be hard to do is quite different from the objection to Freud's theories, wherein a man who e.g. didn't appear to have any Oedipal concerns would just be said to be suppressing or projecting them or whatever. Marxism, too: Lenin wrote a book about how Marx's theory's failure to materialize was just a further proof of how right he was about the evils of capitalism. These theories aren't falsifiable because they let you just tell another story about how they were right all along. 

Yes, the instrument could be wrong; do it again. But if there's not a fact of the matter that could falsify a theory if known, it's not science.

The second problem with Popper’s proposal has to do with the actual demarcations it gives us. The very minimum we should expect from a demarcation criterion is that it slices the sciences in the right places. We want our criterion to recognize as scientific those theories that are very generally accepted as hallmarks of contemporary science, such as quantum physics, natural selection, and plate tectonics. At the same time, we want our criterion to rule out doctrines such as astrology and dowsing. Popper’s falsifiability standard is not especially helpful in this regard. For starters, it is difficult to present the “historical” natural sciences, such as evolutionary biology, geology, or cosmology—those fields where we cannot “run the tape again” in the laboratory—exclusively in terms of falsifiable claims. Those sciences provide persuasive explanations of nature through the totality of a narrative chain of causal inference rather than a series of empirical yes-no votes. Popper thus inadvertently excludes important domains of contemporary science.

I would argue that this is also a terrible objection. To say that you want to "slice the sciences in the right places" indicates that you think you already know where the slices should be made. Actually, Popper raises an important objection to theories even from these widely recognized fields: they aren't doing quite the same thing as the sciences that can provide replicable testing, and their theories remain rather more theoretical as a consequence. They're not in the same category as Marxism, but maybe that only means that there is Hard Science, and then degrees of distance from it. I'm inclined to score this Popper 2, objections 0 so far.

The situation with inclusion is even worse. The difficulty was sharply expressed by philosopher of science Larry Laudan in an influential article from 1983. Popper’s criterion, he wrote,

has the untoward consequence of countenancing as “scientific” every crank claim that makes ascertainably false assertions. Thus flat Earthers, biblical creationists, proponents of laetrile or orgone boxes, Uri Geller devotees, Bermuda Triangulators, circle squarers, Lysenkoists, charioteers of the gods, perpetuum mobile builders, Big Foot searchers, Loch Nessians, faith healers, polywater dabblers, Rosicrucians, the-world-is-about-to-enders, primal screamers, water diviners, magicians, and astrologers all turn out to be scientific on Popper’s criterion—just so long as they are prepared to indicate some observation, however improbable, which (if it came to pass) would cause them to change their minds.

OK, that one's better. Popper's criterion may not be sufficient to exclude fields that are easily falsifiable because they are crazy. We might need to address that objection to have a proper definition of hard science. That seems to be the evolving position, and it's not that hostile to Popper: he said something important, but he may have mistaken that something for everything.

Other approaches might prove more successful. Philosopher and former professor of biology Massimo Pigliucci, for example, has suggested that the problem with falsicationism is its one-dimensionality, not its effort to establish clear criteria. Perhaps we could add more dimensions that correspond to the heterogeneity of scientific practice.