The Post Hoc Fallacy

Post hoc, ergo propter hoc means, in Latin “after this, therefore because of this,” which is the name of the fallacy that “because an event occurred first, it must have caused this later event.” (From the Merriam-Webster Dictionary.)

Many commit this fallacy when they credit an improving economy to a current President or Presidential administration. While a President or administration can be a cause or a partial cause of an improving economy, the cause, in part or whole, is usually some set of factors that stretch back years, and has nothing to do with a current President.

And many commit this in blaming a person for some event or some crime, even though there is no causal tie.

But note that, in contrast and on the other hand, causation does mean that events will follow in sequence: there is a before and after. It’s just that “there is a before and after” does not by itself mean there is a causal relationship.

Temporal sequences you can think of as the broader category of which casual sequences are part, just as animal is the broader category of which humans are part.

After you get some bacteria or virus (and given an immune system and animal self not able to fight it successfully), you will get sick. Cause and effect.

After you deplete some key nutrient because of a diet that is not species-appropriate, you will suffer a disease. Cause and effect.

But, on the other hand, trying some diet and claiming, after only a few months, that it makes you feel better so it’s the diet everyone should follow, is not, on its own,. causation. It’s the post hoc fallacy. And “I feel better” is not at all the same as “I am in fact functioning optimally in every human biological parameter.” While being species-appropriate will lead, in normal contexts, to feeling good, “feeling good” is not science or understanding or a whole truth.