context: We doubt that Bernhard is a frog. It is probable that Greg is a rhino. Chances are slight that Fred went to the garden. It is highly unlikely that if either 'Fred went to the garden' or 'Bernhard is a frog' but not both then Jeff dropped the apple. Chances are slight that if 'Fred went to the garden' or 'Greg is a rhino' or both then John picked up the milk. It is highly likely that if either 'Fred went to the garden' or 'Greg is a rhino' but not both then Gertrude is a mouse.
hypothesis: It is impossible that 'John picked up the milk and Jeff dropped the apple'.
valid_hypothesis: It is impossible that 'John picked up the milk and Jeff dropped the apple'.
invalid_hypothesis: There is a very good chance that 'John picked up the milk and Jeff dropped the apple'.
problog: 
    and(A,B) :- A,B.
    or(A,B) :- A;B.
    nand(A,B) :- not(and(A,B)).
    nor(A,B) :- not(or(A,B)).
    xor(A,B) :- or(A,B), nand(A,B).
  
    %hop0
    0.2::factA.
    0.7::factB.
    0.1::factC.
    %hop1
    0.05::factX:-xor(factC,factA).
    0.1::factY:-or(factC,factB).
    0.9::factZ:-xor(factC,factB).
  
    %hop2
    conclusion:-and(factY,factX).
  
    query(conclusion).
    
hypothesis_assertion: 'John picked up the milk and Jeff dropped the apple'.