>"My reasoning here goes like this: the toothbrush is dry; it is unlikely that the toothbrush would be dry if my son had cleaned his teeth; therefore he hasn’t

>"My reasoning here goes like this: the toothbrush is dry; it is unlikely that the toothbrush would be dry if my son had cleaned his teeth; therefore he hasn’t cleaned his teeth." I don't think this works so well because you are jumping from a qualitative statement (dry or not dry) to a quantitative ("at least as extreme").