Another widely used and recognized use of "ergo" is in the Latin expression "post hoc ergo propter hoc" (meaning "after this, therefor because of this). It is in common use by folks who think about reasoning, e.g. philosophers, rhetoricians and their ilk. It describes the logical fallacy of coincidental correlation: the asserton that, because one thing happens after another thing, the second thing was caused by the first thing ... which it wasn't ... necessarily.