Logical Fallacy of the Week, Week 49: Post Hoc Ergo Propter Hoc

I have listed the first two in the past, but I am putting these three together because I think it appropriate, as they always seem to go hand in hand in discussions.  These are three fallacies used by the greenies and lefties constantly.  Once they are recognized they are easily overcome.  RK

Onus probandi – from Latin "onus probandi incumbit ei qui dicit, non ei qui negat" the burden of proof is on the person who makes the claim, not on the person who denies (or questions the claim). It is a particular case of the "argumentum ad ignorantiam" fallacy, here the burden is shifted on the person defending against the assertion…….When debating any issue, there is an implicit burden of proof on the person asserting a positive claim. "If this responsibility or burden of proof is shifted to a critic, the fallacy of appealing to ignorance is committed".   This burden does not necessarily require a mathematical or strictly logical proof, although many strong arguments do rise to this level (such as in logical syllogisms). Rather, the evidential standard required for a given claim is determined by convention or community standards, with regard to the context of the claim in question.

Petitio principii – see begging the question…..The fallacy of petitio principii, or "begging the question", is committed "when a proposition which requires proof is assumed without proof", or more generally denotes when an assumption is used, "in some form of the very proposition to be proved, as a premise from which to deduce it". Thus, insofar as petitio principii refers to arguing for a conclusion that has already been assumed in the premise, this fallacy consists of "begging" the listener to accept the "question" (proposition) before the labor of logic is undertaken. The fallacy may be committed in various ways.

Post hoc ergo propter hoc Latin for "after this, therefore because of this" (false cause, coincidental correlation, correlation…..Post hoc ergo propter hoc, Latin for "after this, therefore because of this", is a logical fallacy (of the questionable cause variety) that states "Since that event followed this one, that event must have been caused by this one." It is often shortened to simply post hoc and is also sometimes referred to as false cause, coincidental correlation, or correlation not causation. It is subtly different from the fallacy cum hoc ergo propter hoc, in which two things or events occur simultaneously or the chronological ordering is insignificant or unknown.

Post hoc is a particularly tempting error because temporal sequence appears to be integral to causality. The fallacy lies in coming to a conclusion based solely on the order of events, rather than taking into account other factors that might rule.......