Fallacy. This word is sometimes used as if it were merely synonymous
with error. It properly means, however, something which causes error,
and technically denotes an inaccuracy in reasoning which vitiates the
process and invalidates the conclusion.
Though not to be distinguished in itself from a
sophism, I think that in these latter days we generally denote by
fallacy a defect in the reasoning which is unobserved by the reasoner
himself, and deceives him as much as anyone else, and by sophism a trick
played of set purpose to bewilder another.
The generic name for fallacies and sophisms of every
sort is paralogism, a transgression of logical of logical laws.