The most obvious arrangement would be to place the writers in groups, according as they manifest a tendency toward atheism, pantheism, deism, or rationalism,(902) respectively; but the mode which more nearly accords with our general purpose would be to adopt a philosophical rather than a theological classification, and arrange them according to the variety in the tests of truth employed by them, and the sources from which their arguments start, rather than the conclusions at which they arrive. Perhaps the advantage of both plans will be in a great degree combined, if we classify them according to the branch of science, physical, mental, or critical, from which the doubts take their rise. We shall commence with those writers who make sensation to be the last appeal in belief, or whose doubts arise either from the methods or the results of physical science. This class of opinions varies from positive disbelief of the supernatural, generated by the fixed belief in the stability of nature and disbelief of miraculous interference, to merely isolated objections suggested by the conflict between the discoveries of natural science and the statements of holy scripture. The name which most fitly describes the extreme form of unbelief is Positivism.(903) This system of philosophy, already stated to have been invented by Comte, is silent about the existence of a Deity. It inculcates the belief in general laws, and acknowledges the order in Nature, which we are accustomed to regard as the result of mind; but declines to argue to the existence of a designing mind, where the evidence cannot be verified by proof referable to sensation. Nature’s laws are in its view the only Providence; obedience to them the only piety. A few minds may be found, which not only accept the positive philosophy, but even receive the religion taught in the positivist catechism.(904) Unable to satisfy the longings of their heart by this system of Cosmism, they receive the extravagant idea of the worship of humanity, which Comte invented in his later days.