False cause fallacy, Post hoc ergo propter hoc

This form of reasoning is also called a false cause fallacy.  It is a logical fallacy that establishes a causal relationship that is not there at all. It is a very commonly used tactic. So much so, that even the Romans recognised it. The post hoc refers to the Latin phrase “post hoc, ergo propter hoc,” which translates as “after this, therefore because of this.”

It is good to recognise that correlation isn’t the same thing as causation. An event is correlated when there some level of relation between two or more events, but one is not necessarily causing the other.

For instance: Mary and John used to be in a relationship, and were at the same party. They had words in the buffet line, and John leaves early.

Obviously, there is a correlation between these events: they were ex-partners, and at the same party, they had a fight, and John left early. It would be a causal fallacy though to presume that John left early because of the fight. It is a possiblity, of course, but maybe he had an early meeting the next day, or went on to another party.

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