Contraposition

Contraposition is a transformation in categorical (Aristotlean) logic. It involves two steps:

1. Switch the subject and predicate terms.
2. take the complement of both terms.

For example, assume the A-Type sentence ‘All 4-chan users are trolls.’ (in common language, ‘everyone on 4-chan is a troll!’) If we transform this with contraposition we turn it into:

1. switch the subject and predicate terms: ‘All trolls are 4-chan users’
2. take the complement of both terms: ‘All non-trolls are non-4-chan users.’

Related posts:

1. Contraposition A
2. Contraposition I
3. Contraposition E
4. Venn Diagram tool coming soon
5. Obversion A