Now an apparent refutation depends upon the elements involved in a genuine one; for the failure of one or other of these must make the refutation merely apparent, eg that which depends on the failure of the conclusion to follow from the argument (the argument ad impossibile) and that which treats two questions as one and so depends upon a flaw in the proposition, and that which depends on the substitution of an accident for an essential attribute, and a branch of the last that which depends upon the consequent; moreover, the conclusion may follow not in fact but only verbally; then, instead of proving the contradictory universally and in the same respect and relation and manner, the fallacy may be dependent on some limit of extent or on one or other of these qualifications; moreover, there is the assumption of the original point, in violation of the principle of not reckoning in the original point.