the machine-or-transformation test as the sole test of patent eligibility, saying that rather it was simply a "useful clue." The 5-4 majority refused to hold that all business methods were incapable of being patented, but four justices would have established such a rule. A concurring opinion pointed out that the Court was unanimous, however, as to many issues in the Bilski case, including a rejection of the Federal Circuit's late 1990s State Street Bank decision, which allowed patents on any advance, technical or nontechnical (and in that case a numerical financial calculation of stock price changes) that produces a "useful, concrete and tangible result." The Supreme Court's Bilski decision was criticized because of its lack of detailed guidance on how to determine whether a claim was directed to an abstract idea. Nonetheless, it provided some clarification and affirmed the Federal Circuit's taking a new direction in its software-related patent cases. Mayo case In Mayo v. Prometheus, the Supreme Court invalidated a patent on a diagnostic method, because it non-inventively implemented a natural principle; the Court drew on cases involving computer software and other abstract ideas. In this case, the Court was much more detailed in describing how to recognize a patent-ineligible claim to an abstract idea. The Mayo methodology has come to dominate patent-eligibility law. It revived the approach of the Flook and Neilson cases, which is to treat the underlying principle, idea, or algorithm on which the claimed patent is based as if it were part of the prior art and to make patent eligibility turn on whether the implementation of it is inventive. This led to the "two-step" Alice test described next. Alice case At the time the Mayo case was decided, there was some uncertainty over whether it applied only to natural principles (laws of nature) or more generally to patent eligibility of all abstract ideas and general principles, including those involved in software patents. The Alice decision confirmed that the test was general. The Alice case involved patents on electronic methods and computer programs for financial-trading systems on which trades between two parties who are to exchange payment are settled by a third party in ways that reduce the risk that one party performs while the other does not. The patents cover what amounts to a computerized escrow arrangement. The Court held that Mayo explained how to address the problem of determining whether a patent claimed