It's Only Logical
Induction is reasoning from a particular fact to a general conclusion (all sheep we see are white, so all sheep must be white).
Deduction is the reverse — reasoning from a general conclusion to a particular fact (all sheep are white and you have a sheep, so it must be white).
Never get personal in debates. No matter how stupid or evil you really think your opponent is, keep the discussion focused on the issues. If you indulge yourself in what are known as
A bright debater can sound perfectly logical but, because of either ignorance or blind devotion to his cause, can make unsound arguments. Some common ways to make a case that should be avoided:
Quoting a famous person who is not an expert in the area under discussion.
Quoting only a portion of a statement because the full comment or its context do not support the point you want to make.
Using emotionally charged language to incite the audience and blur the argument (baby killer! fascist!). Sometimes this comes in the form of innuendo — the phrase “there are those who seem to want to take away our liberty” could be interpreted as an allusion to the opponent.
Citing an experiment or poll that had an inadequate sample.
Using the results of a survey that used biased questions (“should the candidate who wants to undermine our schools be reelected?”).
Relying on majority opinion — conventional wisdom even among experts is often wrong, so really listen to the points that dissenters raise.
Circular argument — the conclusion assumes something that has not been proven.
Red herring — an argument used to prove something that is really irrelevant, usually to distract the audience from the real issues.
Two wrongs make a right — citing injustices to gain sympathy for one's plans.
Anecdotal fallacy — overestimating the probability of events because of recent experience. Assuming correlation is causation: A came before B, so A caused B (“drug confiscations have come down since our new laws targeting major dealers went into effect, so they must not be selling as much”).
Over-generalization (“gun owners like to kill”).
Straw man — setting up an easy target to knock down, even though the example is not representative of the opponent's actual views.
Using half-truths — facts that sound better for your position if you withhold relevant information.
Selective reporting — pointing to successes and not failures.
Putting a priority on worst-case scenarios, regardless of how improbable.
Only looking at the short-term effects and ignoring the long-term.
False choices — making it seem that there is only your way or ruin, even though other plans may be equally viable.
Asserting your own authority — you have credentials and therefore the audience should assume you are right.
The best way to find out whether the arguments you use rely on improper reasoning is to present them informally to someone who disagrees with the positions you are taking and see how well they stand up to criticism. Better that then to have it happen at the actual debate.