Court looked back to 19th century decisions such as O'Reilly v. Morse, which held that abstract ideas could not be made the subject of patents. Flook case The Court's 1978 ruling in Parker v. Flook, was similar to Benson in principle. The Benson and Flook cases also established that a "clue" to whether a patent might be granted on a process was whether the process was carried out with a particular apparatus or else effectuated a transformation of an article from one state or thing to another state or thing. In Flook, where the sole departure from the prior art was concededly the formula or algorithm, no transformation was alleged, and it was conceded that the implementing apparatus was old or conventional, the process was simply not the kind of process that could be patented. The principle, stated in Flook, that to be patent eligible the implementation of an abstract idea or law of nature must be inventive, rather than routine or conventional, became of paramount importance in Supreme Court jurisprudence at the beginning of the 21st century. (This occurred in the Mayo and Alice cases.) Diehr case In the 1981 case of Diamond v. Diehr, the United States Supreme Court upheld the CCPA's reversal of the Patent Office, and ordered the grant of a patent on a process for curing rubber in a mold, a substantial part of which involved use of a computer program that used a well-known formula (the Arrhenius Equation) for calculating the time when rubber was cured and the mold could therefore be opened. The Supreme Court stated that in this case, the invention was not merely a mathematical algorithm, but a process for molding rubber, which used the mathematical formula for an industrial purpose, and was therefore patent eligible. In the Diehr case, there was no concession (as there was in Flook) that the implementation was conventional, and the process did effectuate a transformation of substances (from uncured rubber to cured rubber). The Supreme Court later explained the meaning of this decision and how it actually harmonized with Benson and Flook in the Court's 2012 Mayo opinion. In the Mayo case, the Court explained that Diehr had not simply claimed the Arrhenius Equation implemented in a non-inventive machine but had instead implemented it in a way that the Diehr Court had found inventive. Under this interpretation, Diehr satisfied the requirements that the Court had