Comte, a sociologist, believed in a three part model of human knowledge. He claimed that it had gone through phases. There was a religious worldview, and a metaphysical worldview before the scientific interpretation was considered. The positivistic method should, said Comte, no longer aim at a revealing ultimate causes. It should rather focus on how data are linked together. Scientists would simply interpret these correlations. All human knowledge could only be relatively true, so Comte with a look at these interpretations. Late 19th-century philosophers of the sciences from Heinrich Hertz to Ernst Mach eventually discussed specific requirements of operable scientific theories and physical laws such as the predictability of results in experiments and the functionality of laws in computations.