public static Stella_Object standardizePropositionTree(Stella_Object tree) {
    if (Stella_Object.stringP(tree)) {
      tree = Stella.readSExpressionFromString(((StringWrapper)(tree)).wrapperValue);
    }
    tree = Logic.standardizeLogicalParseTree(tree);
    if (Stella_Object.consP(tree)) {
      tree = Logic.canonicalizePropositionTree(tree);
    }
    return (tree);
  }