ABSTRACT
This paradox was known in the Middle Ages. It is found, for instance, in the fourteenth-century writings of Pseudo-Scotus, who showed how to derive an arbitrary conclusion from inconsistent premisses. Here is an example:
(1) Pat is both a mother and not a mother (2) Pat is a mother, from 1 (3) Pat is a mother or Pat is a father, from 2 by the principle
of addition (‘or’ here is inclusive, it means ‘and/or’. An inclusive ‘or’ statement, A or B, is true provided at least one of its disjuncts, A, B, is true.)
(4) Pat is not a mother, from 1 (5) Pat is a father, from 3, 4, by the principle of disjunctive
syllogism.
