context: It is probable that Brian is a swan. Chances are about even that Sandra took the milk. It is highly unlikely that Mary left the football.
hypothesis: There is a very good chance that brian is a swan, and Sandra took the milk.
valid_hypothesis: It is probably not the case that brian is a swan, and Sandra took the milk.
invalid_hypothesis: There is a very good chance that brian is a swan, and Sandra took the milk.
hypothesis_assertion: Brian is a swan, and Sandra took the milk.