Last night at council I referred to seeing what I believed was a post hoc fallacy in a report, or more properly a post hoc ergo propter hoc fallacy. Yeah, I probably annoyed some folks in the audience because I used Latin words and that confused them. But hey, they already think I’m a jerk because I can spell words like egregious and nefarious without using spellcheck, so I doubt I lost any votes over it.
It means an error in assigning a causal relationship between two or more coincidental events. For example:
- I combed my hair a different way and I came down with a cold.
- After a few days, I combed my hair the old way and the cold went away.
- Therefore combing my hair a different way gave me a cold.
This is an easy one to see through, but you’d be surprised how many people apply this logical fallacy to their thinking. For example, the typical chemtrail conspiracy theory:
- I saw contrails from a plane overhead.
- My skin got itchy afterwards.
- Therefore the government is spraying something from jet planes that is making me sick.
Which pretty much sums up the whole nonsense around chemtrails. People naturally look for events that explain what they already believe to be true (confirmation bias). When causality does not exist between events, what you often find is merely wishful thinking.
…the most general fallacy of reasoning to conclusions about causality. Some authors describe it as inferring that something is the cause of something else when it isn’t, an interpretation encouraged by the fallacy’s names. However, inferring a false causal relation is often just a mistake, and it can be the result of reasoning which is as cogent as can be, since all reasoning to causal conclusions is ultimately inductive.