context: Chances are about even that Julius is white. It is probably not the case that Brian is a lion. It is improbable that Sandra got the football. It is impossible that if Julius is white, and Sandra got the football, then Yann is thirsty. There is little chance that if Julius is white, or Brian is a lion, then Greg is a swan. There is a very good chance that if either Brian is a lion, or Sandra got the football, then Mary went to the garden.
hypothesis: It is impossible that sandra got the football, and Greg is a swan.
valid_hypothesis: It is impossible that sandra got the football, and Greg is a swan.
invalid_hypothesis: It is certain that sandra got the football, and Greg is a swan.
hypothesis_assertion: Sandra got the football, and Greg is a swan.