Conjunction of a
statement and its
A contradiction in logic is never
true, and thus deriving a
contradiction from a set of statements shows one or more statements in
the set are not true. See
reductio ad absurdum.
Note this is a linguistic notion.
Hegel and his followers (Marx, Lenin) introduced a lot of obscurity,
nonsense, and indeed contradiction in their philosophy by claiming that
there really are contradictions in reality. At best, this confuses
oppositions and contradictions.