context: Chances are slight that Gertrude is a mouse. There is a very good chance that John left the apple. It is unlikely that Lily is gray. There is a better than even chance that if Gertrude is a mouse, or Lily is gray, then Brian is a swan. There is little chance that if either Gertrude is a mouse, or John left the apple, then Greg is a rhino. It is unlikely that if John left the apple, and Lily is gray, then Julius is a frog.
hypothesis: It is impossible that brian is a swan, and Greg is a rhino.
valid_hypothesis: It is impossible that brian is a swan, and Greg is a rhino.
invalid_hypothesis: Chances are about even that brian is a swan, and Greg is a rhino.
hypothesis_assertion: Brian is a swan, and Greg is a rhino.