But first, exactly what is a logical fallacy?
A logical fallacy is, roughly speaking, an error of reasoning. When someone adopts a position, or tries to persuade someone else to adopt a position, based on a bad piece of reasoning, they commit a fallacy.We see them and are exposed to them all the time. Many are harmless, but others can be wielded as a weapon to force a shift in perception or opinions about topics of importance, even when the 'new paradigm' is woefully inaccurate or an outright lie. We've seen that time and time again throughout history, the two biggest examples being the rise and fall of both Nazi Germany and Communism, specifically as practiced in the defunct Union of Soviet Socialist Republics. Logical fallacies were used to drive the people of both nations in the directions their leaders wanted, even if the outcomes were abhorrent and, dare I say, genocidal. We still see it today in places like Venezuela, where deliberate logical fallacies have been used to control the perceptions of the people until the point where they could no longer ignore them. The nation's economy is a shambles, caused by the ideological blindness of those in power. They used all kinds of logical fallacies to convince the people that on Chavismo, the Venezuelan version of socialism could 'save' them from the predation of the 'Capitalist Yankees', all while driving the population into wide spread poverty and taking control of the wealth for the 'good of the Venezuelan people'.
There are a number of different types of logical fallacies, all based upon the type of reasoning used to create and support them. They run the gamut from formal (deductive) fallacies, informal (inductive) fallacies, and logical/factual error fallacies. I could try to parse them here, but it would be easier if you go to the site linked above and read the various descriptions there.
Probably the two most common logical fallacies we run across are the Straw Man Argument and the Appeal to Authority. We see both of these an the 'Net, in the Letters to the Editor in our newspapers, and even in debates amongst acquaintances. We've certainly seen a large number of examples of both of these during the ongoing debate about climate change.
The first is used when one's position is weak in order to make it appear as if it is stronger. The second is used most often when there is no “there” there so the argument is redirected towards the opinions of an authority figure even if that person has little or no real expertise in the subject being debated or has been proven wrong.
If we understand logical fallacies we can both protect ourselves against those used by others and prevent ourselves from using them ourselves.