 If two people are arguing ‘If \(p\) will \(q\)?’ and are both in doubt as to \(p\), they are adding \(p\) hypothetically to their stock of knowledge and arguing on that basis about \(q\); so that in a sense ‘If \(p\), \(q\)’ and ‘If \(p\), not \(q\)‘ are contradictories.