Thursday, May 04, 2006

Logical Fallacies

Am beginning to realize that blogging sets you up very nicely for publishing a book. The following is the third book by a blogger in the last couple of weeks alone to go on my usually thrifty wish-list. The thing is, when you relish reading someone's blog, you just have to rush out and get their book. We always enjoy Madsen Pirie's contributions to the Adam Smith Blog, so when we hear he has written a book on logical fallacies entitled "How to Win Every Argument: the Use and Abuse of Logic", well who could resist!

Dr Pirie gives us a good taster in a Spectator article:

"It is actually worth the trouble to identify the invalid forms of argument, and to learn their names. Not only can you then avoid them yourself; you can also identify them in opponents. If you call your opponent's errors by their Latin names, you can make it look as though he or she is suffering from a rare tropical disease.

"A favorite in daily use is called cum hoc ergo propter hoc. It is the supposition that events which occur at the same times must be causally connected. Thatcherism can be linked with rising crime, increased alcohol consumption, greater popularity of country and western music, and just about anything that happened in the 1980s. To use this yourself in argument, all you have to do is ask sarcastically if it was just a a coincidence that the one event accompanied the other. When you hear others using it, though, just ask them to show you the connection
. "

There are loads of other similarly anatomized fallacies - one I have suffered from recently - 'tu quoque' where your criticism is deemed too inconsiderable to be worthy of a direct response because of something that you yourself allegedly once did.


Anonymous said...

How incredibly useful! Am often having to deal with the most extraordinary illogical lines of reasoning.
(cough, I do indulge in the cum hoc ergo propter hoc myself e.g. violent crime in the streets in Cheltenham has apparently risen 40% since extended licencing hours...would be interesting to know how to avoid such causal relationships!)

However, unfortunately, the library doesn't own even one copy of this book, countrywide from what I can gather. So I shall just hope that you can come up with a few more of the more frequently used logical fallacies!


Maia said...

D - I think cum hoc ergo propter hoc is OK if you are only using it to raise the possibility of a connection.

It is only evidence, though, not proof. And how weighty the evidence is depends on the circumstances.

For example the inherent likelihood that more drinking will lead to more violent street crime, coupled with the absence of any other ready explanation for a sharp rise in crime... These circumstances mean that the evidential weight of the contemporaneity is stronger than it would have been if - say - there was also a strong possibility that increased crime had been caused by massive cuts in police presence (hypothetically speaking).

Carlotta said...

Yes...I suppose you could say that 'cum hoc ergo propter hoc' is a logical fallacy insofar as it implies an explanation without one actually being there.

The explanation for the contemporaneity of events could be genuine though.