context: It is impossible that Mary is in the park. It is almost certain that Julius is a swan. We doubt that John discarded the milk. There is little chance that if Mary is in the park, or Julius is a swan, then Bill dropped the milk. It is probable that if Julius is a swan, or Mary is in the park, then Greg is green. There is little chance that if either John discarded the milk, or Julius is a swan, then Brian is green.
hypothesis: It is impossible that brian is green, and Mary is in the park.
valid_hypothesis: It is impossible that brian is green, and Mary is in the park.
invalid_hypothesis: Chances are about even that brian is green, and Mary is in the park.
hypothesis_assertion: Brian is green, and Mary is in the park.