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. 
Again, the attempt might be made to turn against me my own criticism of the inductivist criterion of demarcation; for it might seem that objections can be raised against falsifiability as a criterion of demarcation similar to those which I myself raised against verifiability.
This attack would not disturb me. My proposal is based upon an asymmetry between verifiability and falsifiability; an asymmetry which results from the logical form of universal statements. For these are never derivable from singular statements, but can be contradicted by singular statements. Consequently it is possible by means of purely deductive inferences (with the help of the modus tollens of classical logic) to argue from the truth of singular statements to the falsity of universal statements. Such an argument to the falsity of universal statements is the only strictly deductive kind of inference that proceeds, as it were, in the ‘inductive direction’; that is, from singular to univeral statements. 
Repudiate bullshit wherever you find it. Reason is worth standing up for.
But be smart about it. Instead of telling people they’re espousing nonsense, ask why they believe what they believe. Then really listen. Be genuinely open to changing your mind. Ask thoughtful questions. Examine the reasoning process that led to their conclusions. Keep your cool. Probe. Then hone in and expose instances of unreason.
What we want to do is create a culture where we take responsibility for what we say, what we think, and what we do. Education isn’t just about you, it’s about the environment around you.
Throughout the history of advocacy and controversy the approach even of polemicists of genius, like Voltaire, has been to seek out and attack the weak points in an opponent’s case. This has a severe disadvantage. Every case has weaker as well as stronger parts, and its appeal lies, obviously, in the latter; so to attack the former may embarrass its adherents but not undermine the considerations on which their adherence largely rests. This is one of the reasons why people so rarely change their views after losing an argument. More often such a reverse leads eventually to a strengthening of their position, in that it leads them to abandon or improve the weakest parts of their case. It often happens that the longer two intelligent people go on arguing the better each side’s case becomes, for each is being all the time improved as a result of criticism. The Popperian analysis of this is self-evident. What Popper aims to do, and at his best does do, is to seek out and attack an opponent’s case at its strongest. Indeed, before attacking it he tries to strengthen it still further. He sees if any of its weaknesses can be removed and any of its formulations improved on, gives it the benefit of every doubt, passes over any obvious loopholes; and then, having got it into the best-argued form he can, attacks it at its most powerful and appealing. This method, the most intellectually serious possible, is thrilling; and its results, when successful, are devastating. For no perceptible version of the defeated case is reconstructable in the light of the criticism, every known resource and reserve of substance being already present in the demolished version. [91-2]
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. 
Dawkins has somehow become the public defender of scientific rationality against, of all things, creationism, and more generally against a pre-scientific world-view that has been obsolete since Galileo. The frustrating thing about all this is that, so long as the proponents of our best theories of the fabric of reality have to expend their intellectual energies in futile refutation and re-refutation of theories long known to be false, the state of our deepest knowledge cannot improve. 
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]