Philosophy again rears its head.
…as in Sir Karl Popper (1902 – 1994), an Austrian philosopher of science who rejected the traditional idea that science advances by observation, deduction, and proof (Horgan, 1992). Instead, Popper held that knowledge advances through a creative process of developing theories which are filtered out by falsifiability: This means the ability of a theory—a working framework for explaining and predicting natural phenomena—to be disproved by an experiment or observation (Popper, 1959). The principle weakness of this approach is that Popper held that knowledge advancement was an evolutionary process.
Well, Popper was partially correct.
What Popper meant was that the theories that survive are the ones that best help us survive and prosper. When a theory is tested, we consider how it fits with our overall belief system and reject the theory that is most expendable – the one with the least inductive evidence supporting it. This is like cross-pollinating and irradiating your roses over generations to create the black rose that your aesthetic taste has desired. Or think of scholars in the 16th Century, trying to force-fit explanations of the jinking movements of planets in the sky to the Catholic Church’s Earth-centric world view. This is not really how science works. Falsifiability is crucial, yes. However, convenience – forcing a theory to conform to our existing belief system – no, that’s not seeking Truth. That’s taking the road most easily traveled.
Thomas Kuhn (1922-1996) argued forcefully that science advances only through a process of observing anomalies that don’t fit with existing theories (Kuhn, 1962). These inevitably lead, through a “paradigm shift,” to a newer theory. Willard Quine (1908 – 2000) and Pierre Duhem (1861 – 1916) had earlier laid out a weakness of Popper’s approach – they were certain that hypotheses can never be falsifiable in isolation. Any scientific theory is really an interdependent set of theories and assumptions, where any anomalous observation can falsify a number of different sub-hypotheses. Falsifiability proceeding this way is closer to how modern science really works (Harding, 1976).
There are also hypotheses that are not falsifiable by definition: the existence of a multiverse, the existence of God, the existence of 11 dimensions, etc. Because these things are not falsifiable – cannot be tested experimentally – string theory and belief in God are not science.
Trying to call them science is why science has developed a (hopefully temporary) bad name for itself.
But we must give credit to Karl Popper: because of him, (most) scientists at least try to be honest, and we can now more readily throw out “science” that is not science.