Quora Answer : What are some critiques within the philosophy of science of Popper's principle of falsifiability?
Let's preface by saying that I'm a Popperian. I regard myself as a Critical Rationalist and consider that this is the right approach to thinking about thinking and knowledge. It resolves many problems in epistemology and offers a comprehensive and ethical way to approach the world as an epistemic agent.
Popper's "falsificationism" obviously can't do what it's naively billed as being able to do, which is to put science on the "respectable" basis of logical deduction rather than the less respectable logical induction.
It can't really eliminate some kind of speculative "inductive" / generalizing component to delivering our scientific results.
Let's take a really simplistic example : suppose we conjecture that all y particles follow the Y-Law. And so, if we see a y particle that violates the Y-Law then we know that our Y-Law conjecture is falsified.
OK. But how do we know that we were really observing a y particle in the first place? And not a very similar y' particle that acts like a y in most circumstances but not this one? The answer is, we have to conjecture it. So all our observations that potentially kill the Y-Law hypothesis are, themselves dependent on the "this is a y, not a y' " conjecture. And what is THAT conjecture based on? Probably on a series of previous observations of the particle or the particle generating apparatus which lead us to assume that it's a y generator and not a y' generator. In other words ... on induction.
This is just one way to phrase the problem. You can find this kind of take-down in more rigour from people like Hilary Putnam. And I'd guess it's implicit in Nelson Goodman.
Just a note on that previous answer. In a sense, by asserting the primacy of conjecture in science, Popper is trying to encapsulate and make explicit all the awkwardness and untrustworthiness that is lurking within induction
Induction is a slippery and untrustworthy. People who claim that inductive method X is the right or reliable one don't really have a leg to stand on. So why not just spell that out. Admit it? Say, "sure, there's an element of this alleged claim to knowledge that's just speculative guesswork"? But by making it explicit and being honest about it we are less likely to be caught out by it.
More : ConjectureIsBlind
Quora Answer : Can a claim be both true and non-falsifiable (in the sense of Karl Popper)?
Popper's "falsifiability" criteria is only relevant to empirical / scientific claims. Popper doesn't believe that all knowledge is scientific. He accepts both mathematics and philosophy which don't make empirical claims and don't need to be falsifiable.
However, he has a more general (and I'd argue more important to understand) epistemological position which is that for you to hold knowledge rationally you have to be open to criticism of it. This is where the term "CriticalRationalism" comes from.
Now "falsifiability" in science is just a special case of openness to criticism. One that's relevant to empirical knowledge. If the world behaves differently from your predictions then nature is giving you some important criticism and you ought to be open to it. But other disciplines have their own kind of openness to criticism. In maths, it's by proof. In philosophy, a good argument, etc.
So Popper certainly believes that there are domains like philosophy where scientific falsifiability isn't relevant. (See all the times he gets tetchy when people try to be clever by asking if the falsifiability criteria is falsifiable. Of course it isn't you idiot! It's a philosophical claim. Grrr!)
Now could a claim in some domain be both true AND there be no way to criticize it? My interpretation would be that Popper would say that it's possible, truth is an independent property of a claim, unrelated to how we hold it; but that an agent that held a belief without the capacity to revise it if the right kind of criticism came in would not be rational but instead dogmatic (the opposite of rationality for Popper).
Now does Popper believe that there are any assertions that can't in principle be criticized in some form ... whether by evidence or argument? Probably not. I don't think we have reasons to think that there are. (Though it would be interesting to know what Popper thought of Descartes inability to doubt that he was thinking. I haven't read anything about his position on that.)
Quora Answer : Does Science Really Know What is True?
No. It knows what is False. And what's still undecided.