What fallacy is it ? hasty generalization or begging the question ? Is it really a fallacious argumnet or a valid one ?
Premise1- If A is true, then B is true.
Premise 2- A is true.
Conclusion- B is true.
We have no empirical evidence for supporting P1 and P2 therefore both are false. Since 1 or more than 1 premise is false, the conclusion will always be false. A guy argues that it is a valid argument. On the other hand, I say it is not a valid argument. I don't know which informal fallacy it is. Does this argument contain really a fallacy or the other guy is right ?
The argument is valid. That's because in logic, we say that an argument is valid if it's impossible for the premises to be true and the conclusion false at the same time. If two statements A and If A then B really are true, then so is B . If both A and If A then B are false (or better, if at least one of them is), then the conclusion might be true or might be false, but the argument is still valid; the conclusion still follows. You seem to say that if we have no evidence for something, then it's false. But that's not right. Lots of things are true whether anyone knows them. (How many worms were there in the garden plot at noon yesterday? There's only one right answer, but no one happens to know it or even have evidence.) And things can turn out to be false even if we have serious evidence that they're true. And you seem to be saying that if the premises of an argument are false, the conclusion must be false too. But that's not right, and in particular it's not right even for valid...