Why Scientific Theories Cannot Be Disproven
BlueShirt1: "A scientific theory can never be proven because it can never have All the evidence but it is certainly possible on the basis of evidence to disprove a theory. In over 160 years no one has yet been able to disprove the theory of evolution."
(bottom of page)
Thanks to high profile scientistic wackos like Richard Dawkins, who appear to be completely ignorant of the philosophy of science, we hear this kind of rubbish on a regular basis.
Disprove a theory, you say?
For now we will ignore the awkward question of what "THE theory of evolution" is (not unlike God, everyone swears upon its existence; no one seems able to tell me what it is) and speak generically.
It was first pointed out by Pierre Duhem, and later expanded upon by Willard van Orman Quine, that scientific theories are not tested in isolation, but always in conjunction with what are sometimes called "auxiliary hypotheses", or "background assumptions", or "initial conditions", etc., etc.
It's what's known as confirmational holism. What is tested is not a single statement, but a package thereof.
Let us first note that evidence/data never contradicts a scientific theory. That's not how these things work.
What we can say is that evidence sometimes sits awkwardly with a scientific theory. The fancy name for this is "anomaly", and just about every scientific theory you can name suffers from them.
BlueShirt1: Now, what are we supposed to do when evidence sits awkwardly with a pet theory?
Well, one option is to declare the theory falsified (= disproven) and toss it on the trash heap.
Of course, your scientific peers, being the heterogeneous bunch they are, may not share your enthusiasm. There are always other options, e.g.
1. Do nothing at all. Scratch your head and wonder why evidence is so recalcitrant.
2. Instead of declaring your theory to have been disproven, do everything you can to find some way to reconcile the embarrassing evidence with the beloved theory.
This is a routine occurrence. Why, you might suggest there are "unknown forces" at work. You might suggest hidden variables. You might concoct a previously unheard of subatomic particle. You might hypothesize the existence of a previously unknown planet and get yer telescope out. You might conjure up dark matter and dark energy . . .
In the particular case of evolution, you might invent kin selection, or group selection, or higher level selection, or random drift, or you name it.
Conclusion: Theories cannot be definitively disproven. There are always ways to protect a pet theory against falsification.
And they almost always do precisely that.
BlueShirt1: Perhaps a more specific example might help . . .
It was noted, beginning with Darwin himself, that the existence of altruism poses a problem for Darwinian theory.
Think of these poor worker ants, for example, who, not unlike myself, slave their lives away and never get laid.
Given that the fitter are supposed to prevail, and given that altruists are, by definition, less fit than the other selfish bastards, altruism ought to be winnowed out by the merciless action of natural selection shortly after it rears its ugly head.
But altruism appears to be an incontovertible fact.
What a bummer, eh? Who do we do now: declare the theory to be a load of bollocks (=disproven)?
Oh, don't be silly.
What we do instead is declare the theory to be perfectly healthy and invent kin selection. And group selection. And inclusive fitness. And reciprocal altruism. And the prisoner's dilemma . . .
And my head hurts
BlueShirt1: The term "falsification", a synonym for "disproof", is most closely associated with one man, Sir Karl Popper, one of the most influential philosophers of science of the 20th century.
Popper held not only that scientific theories cannot be proven (a fairly standard position nowadays), but far more radically, that scientific theories are never supported to ANY degree by evidence, due to what he saw as the insolubility of the notorious "problem of induction".
The main reason we remember Popper, however, is for his ideas about falsification. On Popper's account, what distinguishes science from pseudoscience, such as astrology or Marxism (his pet examples), is not the certainty, or even probability, of its claims to knowledge, but rather that scientific theories are "falsifiable".
Science, Popper tells us, makes "bold conjectures" which are subjected to "severe tests". Science sticks its neck out, so to speak, places its head on the chopping block, almost flirting with the executioner's axe. Science advances through a process of falsification.
Even today, scientists as well as science aficionados can often be heard echoing Popper's ideas on falsification, despite the fact that these ideas were discredited many decades ago.
Somewhat inconsistently, even Popper himself, for reasons adverted to in the OP, was forced to concede that, when it comes to scientific theorizing, there can be no such thing as a definitive, conclusive, be-all-and-end-all disproof.
"In point of fact, no conclusive disproof of a theory can ever be produced; for it is always possible to say that the experimental results are not reliable, or that the discrepancies which are asserted to exist between the experimental results and the theory are only apparent and that they will disappear with the advances of our understanding."
Karl Popper, "Logic of Scientific Discovery", p. 50
BlueShirt1: The big honcho himself, Albert Einstein, nobody's fool, cautions against simpleminded notions of falsification (= disproof) in science . . .
"For it is often, perhaps even always, possible to adhere to a general theoretical foundation by securing the adaptation of the theory to the facts by means of artificial additional assumptions"
In other words, as I've been saying above, proponents of a cherished theory can ALWAYS resist falsification if they are determined, ingenious, and dare I say, dogmatic enough.
When faced with awkward or embarrassing evidence/data, all you have to do is say (for example) "We're not seeing the full picture yet" or "There must be unknown forces at work", etc., etc.
Or do nothing at all.