Deductive reasoning (B heading)
Preserving truth (B heading)
Other ways to be “reasonable”? (B heading)
Text box: Justifying reason (B heading)
Reason as a filter (B heading)
Appeal to Authority (B heading)
CAPTION: Stethoscope. It is worth trusting a doctor’s medical advice, because a doctor is a recognised authority on medicine. That doesn’t make a doctor an authority on car maintenance, of course.
CAPTION: advertising a or b. The advertising industry often uses celebrities to endorse products, despite the fact that the celebrities in question have no relevant expertise.
The moral is that, when appealing to an “authority”, you need to check several things, including:
If the answer to any of these questions is “no”, you would be wise not to place your trust in the authority in question.
False Dilemma (B heading)
Caption: road sign showing fork in road. In an example of false dilemma, we are presented with just two options when there are, in truth, other alternatives.
Caption: advert products a and b: Salespeople sometimes use false dilemma: “Your choice is to either buy our product A, or inferior product B. So you just have to buy A!” There may be other alternatives, such as buying neither.
Either Peter has a pilot’s license or else Peter is not permitted to pilot a plane.
What is the problem with the second argument? The first premise presents us with two options both of which are false. In the fallacy of false dilemma we are similarly presented with just two options when there are more. We are told that the only alternatives are A or B. The possibility of choosing C is entirely ignored.
Politicians sometimes use false dilemma to try to force us into making a decision we do not in fact have to make. For example, they may say:
So you have to buy Supawhite!
No doubt some other toothpastes that are just as effective - perhaps even more effective - than Supawhite. These alternatives have been conveniently airbrushed out by the salesperson – leaving you with a false dilemma.
The moral is that, when you seem forced to choose between two alternatives, it is often worth checking whether they really are the only available options. Are you being railroaded by false dilemma?
The Post Hoc Fallacy (B heading)
Superstitious people tend to be particularly prone to the post hoc fallacy. But almost all of us fall for this fallacy on occasion. So beware.
Affirming the consequent: Joe’s DIY mistake
One thing that can confuse here is an unacknowledged slide from what is true about what a person believes to the truth of what they believe. Yes, it may be true that I believe Paris is the capital of Germany. It doesn’t follow that my belief that Paris is the capital of Germany is true.
After all, if truth were relative in that way, I could make any claim true just by believing it. That would be convenient. Suppose I want to be able to fly. I can make it true that I can fly just by believing that I can. But of course the truth about whether or not I can fly, or whether or not fairies exist, is not relative in this way. If Joe is claiming otherwise, he is simply mistaken.
- Beware explanations that are really circular, generating a regress.
- Beware category mistakes – wrongly assuming that the sort of thing that can be said of one category of thing can also sensibly be said of another.
- Beware being seduced in by pseudo-profundity.
- We may think up possible examples which, though they do fit the definition of X, are not examples of X. Or,
- We may think up possible examples which, though they do not fit the definition of X, are examples of X.