We doubt that John left the football. It is improbable that Julius is yellow. It is probable that Bernhard is a frog. We believe that if 'Julius is yellow and Bernhard is a frog' then Greg is a rhino. It is highly likely that if 'John left the football' or 'Julius is yellow' or both then Lily is white. Chances are about even that if 'Julius is yellow' or 'Bernhard is a frog' or both then Mary discarded the milk.
It is probably not the case that 'Bernhard is a frog and Mary discarded the milk'.
It is probably not the case that 'Bernhard is a frog and Mary discarded the milk'.
It is probably the case that 'Bernhard is a frog and Mary discarded the milk'.

  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.
  0.1::factB.
  0.7::factC.
  %hop1
  0.75::factX:-and(factB,factC).
  0.9::factY:-or(factA,factB).
  0.5::factZ:-or(factB,factC).

  %hop2
  conclusion:-and(factC,factZ).

  query(conclusion).
  
'Bernhard is a frog and Mary discarded the milk'.