No argument can force us to accept the truth of any belief. But a valid deductive argument can force us to choose between the truth of its conclusion on the one hand and the falsity of its premises on the other. 
Category Archive: Science and the Open Society
Central European University Press: 2000.
Popper did not regard socialism or capitalism or any economic system as an end in itself. He thought that such systems are to be valued—and evaluated—primarily as means toward freedom. The same holds true for political systems. Even democracy should be valued as a means to another end. It may well help us to preserve freedom, but it can never create freedom if we ourselves do not care for it. 
If the purpose of an argument is to prove its conclusion, then it is difficult to see the point of falsifiability. For deductive arguments cannot prove their conclusions any more than inductive ones can.
But if the purpose of the argument is to force us to choose, then the point of falsifiability becomes clear.
Deductive arguments force us to question, and to reexamine, and, ultimately, to deny their premises if we want to deny their conclusions. Inductive arguments simply do not.
This the real meaning of Popper’s Logic of Scientific Discovery—and it is the reason, perhaps, why so many readers have misunderstood its title and its intent. The logic of discovery is not the logic of discovering theories, and it is not the logic of discovering that they are true.
Neither deduction nor induction can serve as a logic for that.
The logic of discovery is the logic of discovering our errors. We simply cannot deny the conclusion of a deductive argument without discovering that we were in error about its premises. Modus tollens can help us to do this if we use it to set problems for our theories. But while inductive arguments may persuade or induce us to believe things, they cannot help us discover that we are in error about their premises. [113-4]
Popper used to call a guess ‘a guess’. But inductivists prefer to call a guess ‘the conclusion of an inductive argument’. This, no doubt, adds an air of authority to it. But the fact that the ‘conclusion’ of an inductive argument may be false even if all of its premises are true means that it is a guess, regardless of what we may or may not like to call it. 
But I think that the greatest obstacles to education for an open society are our own ignorance of how little we know, and our own unwillingness to acknowledge it even to ourselves.
So, instilling scepticism and the critical attitude in ourselves and in our students will not be enough. We will also need to instill the self-critical attitude in ourselves and in our students. And we will need to reverse the contemporary wisdom that says that ignorance is bad, but admitting it is stupid. This is perhaps the greatest obstacle to education that I know. It infects all levels of society, and especially the professorial ranks of academia. 
Deductive arguments force us to choose betweeen the truth of their conclusions and the falsity of (one or more) of their premises. Inductive arguments do not. This, in and of itself, does not show that anything is true or false. But if an argument is deductively valid, then we simply cannot, without contradicting ourselves, deny its conclusion unless we also deny (one or more of) its premises. In this way, deductive arguments enable us to exercise critical control over our scientific debates. 
Faith, according to Popper, is not belief in a theory that we cannot prove. It is belief in a theory that we are not willing to question. 
There can be little doubt that science is a social enterprise. But my own sense is that trying to base it upon solidarity and communalism is a big mistake. Solidarity and communalism undoubtedly have their charms. But they are still, as they have always been, the primary threat to the freedom of thought. And the freedom of thought, in my view, is what science and philosophy are really all about. 
But shouldn’t an expert’s authority count for something? And isn’t there some appropriate use of authority in critical thinking?
If what I have been saying is true, then courses in critical thinking should teach our students how to criticize authority instead of teaching them how to defer to it. But if this is true, then a statement by an ‘appropriate’ authority should be the first word in a critical inquiry instead of the last. It should be the word that we listen to in order to discover how things stand in a field, what its major problems are, and which of the solutions that have been proposed seem most promising. And it should be the word that we then examine and question and put to the test as we begin to think critically about the field ourselves. I have no doubt whatsoever that this use of authority is very often necessary, appropriate, and reasonable. But it is not an argument from authority. It does not pretend to be good evidence. And it is not presented as a justification of any claim. It would, however, be one that is fully consistent with the goals of critical thinking. 
Most people think that the purpose of an argument is to justify its conclusion — and to thereby establish its certainty — and that the problem with inductive arguments is that they fail to establish their conclusions with objective certainty since their conclusions may be false even if all of their premises are true. But this entirely confuses the issue, and it has even enabled inductivists to take the high ground in the debate, arguing that objective certainty is an impossible dream, and that inductive arguments are not, as a consequence, at fault for failing to achieve it.
But if the uncertainty of their conclusions were the problem with inductive arguments, then we would also have a similar problem with deductive arguments. For the premises of a deductive argument may be false. And the conclusion of a deductive argument may be false as well.
Contrary to what most people think, logical arguments cannot establish the truth, let alone the certainty, of their conclusions. And so contrary to what most people think, the problem with inductive arguments has nothing to do with the uncertainty of their conclusions.
The best that a logical argument can do is test the truth of a statement. But it can do this only by showing that its falsity is inconsistent with the truth of other statements that can only be tested and never proved. Our so-called ‘proof’ methods are really techniques for testing consistency. And the demonstration that a ‘conclusion’ follows from a ‘premise’ shows only that the falsity of the ‘conclusion’ is inconsistent with the truth of the ‘premise.’
That is all that is involved.
But so long as we regard contradictions as unacceptable, it is really quite a lot.
The inconsistency that marks a valid deductive argument — the inconsistency, that is, between the truth of is premises and the falsity of its conclusion — cannot force us to accept the truth of any belief. But it can force us, if we want to avoid contradicting ourselves, to reexamine our beliefs, and to choose between the truth of some beliefs and the falsity of others — because the falsity of the conclusion of a valid argument is inconsistent with the truth of its premises. …
And this is just another way of saying that what we call a proof actually presents us with the choice between accepting its conclusion and rejecting its premises. …
We construct logical arguments in order to persuade others of our beliefs. But the best we can do is to clarify a choice that they have to make. Inductive arguments, however, cannot even do this. [86-7]