(continued...)
In light of the above, let me now address some of the points made by Magical Realist.
Never know. Maybe a few neutrinos got created from cosmic rays interacting with earth's atmosphere or from the big bang or even from the potassium of your own body. Seems we could never rule them out completely.
Right. Maybe pixies each carry around a neutrino or two in their pixie handbags. Anything is possible. Therefore, the bare statement "neutrinos exist" is unfalsifiable and unscientific.
On the other hand, a statement like "If you go into the garden at midnight you will see a pixie with a handbag" is falsifiable. Were we to go into the garden as directed and fail to see the pixie, then this particular pixie hypothesis would be falsified.
Now, suppose you were to say "Ah, but of course pixies don't appear in the garden when human beings are present". Then you're back to the bare claim that "pixies exist (because I say so)", and you're not doing science any more. What if we set up a video camera in the garden? Will that detect the pixies? If so, then we might be back to doing science again. If there's some excuse (pixies are invisible to video cameras), then to be doing science we need a better test.
Remember, the whole point of this "falsifiability" business is to invent a test of the theory that takes risks. It has to be,
in principle, possible that the test - and therefore the theory - will fail.
Magical Realist said:
Right. So the statement "black holes exist", even if defined specifically, is unfalsifible.
No. If defined specifically, the theory is quite likely to be falsifiable. For example "A black hole is defined to be X, Y and Z. If you point your telescope towards P, Q or R, you will find certain objects with characteristics A, B and C. These are black holes, by the previously-given definition."
This theory is obviously falsifiable. If I point my telescope at Q and don't see something with characteristics A, B and C, then the theory, as given, will be proven false. The theory takes a risk by making a very specific prediction.
Take a simpler example. "Water boils at 100 degrees Celcius (under specified pressure conditions)". I can test this statement in many different ways, which is in part what makes it quite a powerful scientific statement. The statement takes an obvious risk. If I have a correctly calibrated thermometer, a stove and a saucepan of water, and I find that under the specified conditions water boils at 47 degrees (or, indeed,
any temperature other that 100 degrees), then the theory is falsified.
The
best theories in science take not just one risk, but many risks. They
could, in principle, be falsified by a multitude of different observations or experiments. And yet, they haven't been, even over the course of hundreds of years and countless numbers of experiments (which can be seen as attempts at falsification).
So what exactly would be a wrong fossil that would falsify man's evolution from apes, given the already abundant evidence we have for that?
Suppose somebody were to discover in a cave somewhere evidence of a truly alien species. Suppose the DNA is analysed and compared to human beings and apes, and it is found that human DNA, but not ape DNA, contains the "alien" DNA. Then, the theory that humans evolved
solely from apes would be falsified.
Coming back to the real world, it should be noted that there are hominid fossils that have been found that have turned out
not to be ancestors of modern human beings. At one time, the theory that these fossils did represent human ancestors would have been a live possibility. But the science made specific predictions. If you test X, and these fossils are human ancestors, you will find Y and you won't find Z. See the risk? At some point, for these particular fossils, the theory was actually falsified. But it was
falsifiable right from the start, before any tests were done. (See the difference?)
So how exactly would you falsify the claim that there is dark matter in my garage? And how would this be any different from saying there is an invisible dragon in my garage? In both cases we are positing entities that are undetectable. Hence they are both unfalsifiable. Not detecting it iow would not prove it isn't there.
The theory of the dragon says that there's a dragon
only in your garage
. The dragon has no other effects other than in your garage, presumably. In fact, when we start drilling down we find that the dragon doesn't actually seem to do
anything detectable. The theory that the invisible, impotent dragon is in your garage takes no risks. No test is suggested that could ever prove it false.
On the other hand, the theory of dark matter specifies tests that go beyond the confines of your garage. It says, for example, that if you look at the rotation curves of galaxies you will see a particular shaped curve that cannot be explained without postulating invisible mass. The specific distribution of dark matter has not yet been pinned down. It is possible that dark matter does not actually exist in your garage, though it is also possible that it does. Part of the task of scientists is to nail down tests to decide such questions one way or the other.
The point about dark matter is that the theory of dark matter is
already taking other risks, even if right now we have no way to directly test whether it is in your garage. Moreover,
in principle there will eventually be a definitive test to see whether there's dark matter in the garage.
If you want to be pedantic, you might argue that "Dark matter exists in my garage" is currently an unfalsifiable conjecture. However, a statement like "Dark matter exists in and around galaxies" is falsifiable right now.
You might like to compare "Alien spacecraft are currently visiting Earth." Is there
any test that would falsify this claim? If not, then it doesn't mean that alien spacecraft aren't visiting Earth. It just means that we're not doing science when we talk about alien spacecraft currently visiting Earth. This is the same as the dragon in your garage. The fact that it is unfalsifiable doesn't mean the dragon doesn't exist. It just means the dragon is not a scientific theory.
No...realizing falsification is a completely superfluous action after a claim has already been verified does not help me understand falsifiability any better.
Are you unable to distinguish the state of verification of a theory before it is tested from the state after such a test?
It remains the nonsense it was when Popper first proclaimed it.
It's a useful idea. It has numerous problems. It is not the be all and end all of deciding what is science and what isn't. But when you're just starting out in the philosophy of science, it's an important idea to start with. One thing it certainly isn't is nonsense. If you think it's nonsense then you're either closed-minded or you're not getting it.
There are scientific claims that are unfalsifiable, and there are unscientific claims that are falsifiable.
Can you give us a few examples?
There is even a distinction to be made between testable and falsifiable.
Please explain the distinction.
I understand falsifiability well enough to know it fails as an adequate standard for deciding anything about a claim or a theory.
What it is supposed to help with is the demarcation between science and non-science. It does not decide whether claims or theories are true or false. Do you understand that?
