(( A re-post of a blog entry I posted elsewhere a while back ))

Yesterday, a couple of co-workers were talking about current events, and one of them said ‘Well, there are two sides to every story, and I’ll listen to them both.’

This got me thinking of the assumptions inherent in such a statement, and the fallacies that can and often do appear in such discussions.

The first and most obvious potential fallacy is right in the statement itself. Two sides. Either-or. Known as the False Dichotomy fallacy, is assumes that there are only two possible sides or positions on the topic. It would be like saying that a politician can only be a Republican or a Democrat, or that a credit card has either a zero balance or is completely maxed out. Clearly, there are additional possibilities for both of those situations. But in so many cases, people tend to assume the ‘two sides’ presentation as a given.

As an example, lets take climate change. I’ve heard various people say several times that either humanity’s pollution and industrial output is the major or even sole driving force behind the current change in global climate, or that humanity’s activities have negligible impact on the global climate. In either case, no mention is made of other possibilities, such as the fact that humanity’s addition to the world’s CO2 levels might be combining with other, non-human, factors to bring about a change in climate, or that perhaps the globe was heading in the current direction already, but our additions have accelerated the process.

Frankly, the all or nothing choices seem to both be clearly flawed, chosen more for their emotional impact or to fit in with preconceived conclusions than from any attempt to discover the actual state of events. This tends to manifest itself as very black and white thinking, fostering a ‘with us or against us’ point of view. In the above example, both the propositions that mankind is solely responsible for the changing climate, and that mankind has no affect on the climate whatsoever, are both clearly untenable. Therefore, both ’sides’ (and I use the term advisedly) can use the false dichotomy to bolster their own position. “Man clearly can’t be solely responsible for the planet’s weather, so we’re not having any effect.” or “Obviously we have to have some effect on our environment, therefore climate change has to be caused by our activities.”

The obvious answer to both statements is, of course, that the truth is probably much more complex.

This brings me to my next thought. A common fallacy is to assume that all sides of an argument are equally true or must be given equal weight. Given two possibilities, A and B, one cannot assume that the chance that A is the correct possibility is the same as the chance that B is the correct possibility. The evidence supporting each option must be considered and weighed, and the probability of each option assessed. Arguments with more and better evidence are given more credibility and more weight, while arguments with less or flawed evidence are diminished and given less consideration. Arguments with no evidence at all should not be considered as valid until such time as they acquire some.

Let’s say that two proposals are made:

* That the Earth is round (well, an oblate spheroid), orbits the sun, and floats in space.
* The Earth is flat, is stationary while the sun orbits it, and rests upon the backs of giant turtles.

Given the mountain of evidence for the first proposal, and the paucity of evidence for the second, it would be madness to consider them equally likely. Yet every day, people make this fundamental mistake, in all walks of life. Evolution/Creationism, Medicine/Homeopathy, 4.5 billion year old Earth/6000 year old Earth, Astronomy/Astrology.

An essential part of rational thought is to weigh the evidence and to recognize that not all ideas are created equal. They thrive or die depending on how well they match up with the evidence.

Views: 31

Comment by Aurie Elizabeth on February 18, 2009 at 12:56pm
I really like this post. I have been studying specific types of logical fallacies lately, but I hadn't quite taken it that far or that in detail yet. :) Nice re-post. I demand more!


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