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Invalid Logic

Entry 826, on 2008-08-04 at 20:57:51 (Rating 3, Skepticism)

Today I have encountered several different sources which use the same type of invalid logic to try to advance their point of view. The trick they used was to suggest that conventional knowledge (usually science) has made occasional errors or doesn't fully understand something, therefore an alternative world view or hypothesis must be true. It sounds ridiculous when I describe it like that, but that's exactly what they are doing.

The first example involved global climate change. I saw this in a letter to the local newspaper where the writer had said that science occasionally gets things wrong and cannot even predict the weather, therefore why should we take any notice of predictions of climate change.

OK I agree, weather is a chaotic system and cannot be predicted reliably - but weather isn't climate. We can make predictions on the bigger picture (climate) where specific predictions on shorter scales (weather) fail.

And most of the examples people give of failure in science aren't valid. For example, they cite the replacement of Newtonian physics with relativity but Newtonian physics wasn't really wrong, it was just less precise than relativity. Another example is scientific support for hoaxes like Piltdown Man. This is misleading because from the very beginning there was significant scientific skepticism about the claim that the skull was genuine. But the facts never get in the way of climate change deniers.

Even if there were significant errors in the past in science (I don't think there were, at least not significant and long lived errors) that doesn't mean we should treat alternative theories with the same degree of credibility as we do scientific ones. The fact is that science is usually right and has provided us with huge benefits through technology. It is true that it could be wrong about climate change but its far more likely to be right and that is the hypothesis we should support unless the evidence (and I mean all the evidence seen as a whole) starts to clearly indicate otherwise.

Another example I heard was a podcast on the existence of a soul and the reality of parapsychological phenomena such as ESP. The person supporting this idea said there was good evidence supporting the reality of consciousness outside of the physical brain. I agree that there is evidence, but a lot of it (maybe all of it) isn't very good, and there is also a lot of evidence showing consciousness actually is a function of the brain.

This person was the victim of perhaps the most common invalid way of supporting a theory: being selective about which evidence to believe and which to ignore, in other words "cherry picking". I find this again and again in relation to religious beliefs, paranormal ideas, political agendas and conspiracy theories. If you pick and choose your evidence then anything can look convincing, even the most outrageous nonsense (such as creationism).

The final error these type of people make, and the most annoying one of all, is their failure to accept facts and change accordingly. The classic example of this are creationists. They use incorrect logic or fake facts to try to prove their point, when these are shown to be false they accept that but then can be seen using the same fake facts next time they try to prove their beliefs. If you want an example ask them about the second law of thermodynamics. They are totally wrong but they still keep pretending it contradicts evolution. What a joke!


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