Absurd consequences

Proving that a position is false, or at least untenable, by showing that if true it would lead to absurd consequences. This is sometimes called a reducio ad absurdum. It is a common and highly effective method of refuting a position.

For example, if someone asserts that anyone who takes a mind-altering drug is a danger to society and should be locked away, then it is easy to refute them by using an absurd consequence move. Alcohol is a mind-altering drug that many of the greatest contributors to western civilisation have used on occasion. Are we then to lock away everyone who has ever used alcohol? Clearly that would be absurd. So we can be confident that the generalisation which lead to the conclusion that we should do so is untenable. It at least has to be refined so that it is clear precisely which mind-altering drugs are supposed to be covered by the term.

Hypothetical questions

Hypothetical questions are used in argument to help show the consequences of acting on a statement. They help to warn against over-generalisation and...

Sweeping statements

...which you should avoid as they can be very easily refuted. And remember there's nothing wrong with hypothetical questions - you can even get into government by answering them!

A political manifesto is a series of promises and solutions that political parties say they'll enact if they are elected, you know – "…what we’ll do to bring down unemployment is blah blah…", that sort of thing. But of course, they’re talking about a hypothetical situation … they haven’t won the election yet!

False dichotomy

This is a misleading account of the alternatives. A dichotomy is a division into two alternatives; for example all fish are either scaly or non-scaly. A false dichotomy occurs when someone sets up a dichotomy in such a way that it appears there are only two possible conclusions when in fact there are further alternatives not mentioned. Sometimes the light isn’t just on or off, there is a whole range in between – like when you use a dimmer switch.

Consistency

Two beliefs are consistent if they can both be true, inconsistent if only one of them can be. If you want to be logical in your argument it is wise to avoid inconsistencies because they can make you very vulnerable in an argument. It’s like saying it’s Tuesday but it’s NOT Tuesday. Two beliefs are consistent only if they both can be true at the same time.

Consistent application of principles means not making special exceptions without good cause. It means you have to examine your principles to make sure you can hold them without contradiction. If you can point out any inconsistencies in statements other people make, it may well cause them to revise their beliefs.

Take, for instance, a topical example. If one country intervenes in a civil war in another one, allegedly on humanitarian grounds, consistency demands that similar action be taken in any relevantly similar case. Lack of consistency might suggest that the first country had vested interests in a particular outcome in the civil war in question and that the given principle was not the real reason for becoming involved. Consistency in argument means everything. If only it did in Foreign Policy…

Take it further

Get to grips with the rights and wrongs as Nigel and guests explore Ethics Bites

Books by Nigel Warburton:
Thinking from A to Z
Philosophy: The Basics
Philosophy: The Classics

If you think you might be interested in studying more about these subjects, find out what the Open University has to offer.

Content last updated: 01/07/2008

About our expert

Born in 1962, Nigel obtained a BA in Philosophy, followed by a PhD in philosophy on the aesthetics of photography from Darwin College, Cambridge. His books include Philosophy: The Basics, Philosophy: The Classics, Thinking From A to Z and Philosophy: Basic Readings.

Nigel's hobbies include writing and marathon running, he is married with one child and lives in Oxford.