theorem
  for S being satisfying_CongruenceIdentity
              satisfying_SegmentConstruction
              satisfying_BetweennessIdentity
              satisfying_Pasch
              satisfying_CongruenceSymmetry
              satisfying_CongruenceEquivalenceRelation
              TarskiGeometryStruct
  for a,b,c,d being POINT of S holds
  a,b <= c,d implies b,a <= c,d by Satz2p4;
