context: Chances are slight that Greg is a swan. It is impossible that John went to the garden. It is probably the case that Mary left the football.
hypothesis: It is impossible that john went to the garden, and Greg is a swan.
valid_hypothesis: It is impossible that john went to the garden, and Greg is a swan.
invalid_hypothesis: It is probable that john went to the garden, and Greg is a swan.
hypothesis_assertion: John went to the garden, and Greg is a swan.