FALLACY

in logic, erroneous reasoning that has the appearance of soundness. Among numerous types of logical fallacies that have been noted, some of the better known are: post hoc ergo propter hoc (after this, therefore, because of this), in which something is assumed to be the cause of something else merely because it was antecedent in time; ad hominem (against the man), attacking an individual rather than establishing pertinent facts; and circulus in probando (arguing in a circle; also called petitio principii, begging the question), attempting to demonstrate a conclusion by means of premises that presuppose that conclusion.