I often come up discussing (peacefully!) with people on a wide spectrum of topics, and equally often I have to debunk flawed arguments, in logic sense (see for example this question).
However I can't just come out with "your argument is not valid in pure logical sense!", because people I usually come up arguing with would just not understand, or worse just call me a weirdo (sigh)
Thus, how should I behave in those cases? Have you any suggestions, or meaningful experiences?
Take the logical fallacy that seems to come up the most: Appeal to Authority. People will make decisions all the time because someone with lots of experience or an important sounding title told them to do so.
I think rather than saying "No Fair! That's the appeal to authority fallacy," you guide the person to the meat of why it's not a compelling argument by asking questions:
Rather than putting some one on the defensive, it allows the other person a chance to make a sound argument.
There is no requirement that you prove the world wrong or correct it. It is the right of everyone to live in their "weird" perspective of the world (as long as it causes no obvious harm).
So if you presented your arguments, revealed a flaw, and the opposite side still sticks with his/her believe, let them be.
Usually, when people argue, they do it to win the argument and not to clarify the truth. Whatever, if their intent is different, it wouldn't be difficult to come to a conclusion.
The best way to show someone that their argument is fallacious is to use a concrete counterexample. For instance, suppose somebody gives you an argument that affirms the consequent. You say something like,
"Your argument is just like this one: `If it is raining, then the street is getting wet. The street is getting wet. Therefore, it is raining.' that isn't right, right? The street could be wet for all kinds of reasons, for instance, somebody might have opened a fire hydrant. All the first sentence guarantees us that if it rains, then the street will get wet, not that rain is the only way a street could get wet."
Most people don't know any logic, but people's verbal reasoning skills are actually sometimes more acute than you might think. (Verbal reasoning is quite a common skill in daily life.)
