“Post hoc ergo properter hoc” = Latin for “Don’t drink the water!”

As a good Catholic girl at Mount Mary Immaculate Academy, I studied Latin for five years in school, and still have a particular affection for this dead language. So does science. Take the medical field, for example, and its common Latin phrase “post hoc ergo properter hoc”, which means “after this, therefore because of this”.

This belief is applied by researchers when they conclude that because a result happened after something else happened, the ‘something else’ must have caused the result.  But in medicine, as in life, we know that correlation does not equal causation.

For example, the weekend before my first heart attack symptoms, I attended a birthday party (my own) where we celebrated the occasion by enjoying lots of very good wine and my friend Lynnie’s gorgeous homemade birthday cake. If correlation did in fact equal causation, we might reasonably conclude that wine and birthday cake are in fact the causes of heart attack.   Continue reading