As the idea of immortality became developed further, the Chinese modified their customs. Instead of offering to the dead material objects, as is still done by many peoples, they came to substitute emblems. “Houses and clothing and food imitated in paper, and dolls of paper and straw to represent slaves, are burned, so that the spiritual forms of these objects may be offered to the spirit they wish to honour.”[173] One of the chief motives of ancestor-worship is fear lest the dead, if neglected, may visit their wrath on the living by sending plagues and pestilence upon them.[174] The worship of the dead had laid hold of the Chinese so firmly that even Confucius, notwithstanding his intelligence and scepticism, paid it a large tribute. “Confucius the philosopher,” said Réville, “regarded it as a duty to offer to his ancestors the gifts of food that princes had sent to him desiring to honour him.”[175] Confucius and his followers were reticent and ambiguous in their references to a future life, but that attitude did not prevent them from “observing the customs and ceremonies as carefully as if they had had a confident faith in the immortality of the soul.”[176] Although Lao-tseu himself believed neither in heaven nor hell, and professed the most rationalistic views, his disciples none the less accepted the doctrine of immortality, and even came to believe in rewards and punishments after death. The followers of Lao-tseu, the Taoists, devoted themselves specially to the problem of immortality. They made efforts to discover an elixir that would be capable of prolonging earthly life to eternity. “One of the chief claims of Taoism,” wrote Réville, “was the possession of a specific against death. It was true that they admitted this to be not only very difficult to obtain, but still more difficult to employ. However, if certain rules were observed strictly they were at least confident of great prolongation of life. It was only the very few Taoists who had reached perfection who could hope to pass into the better world without being subjected to the pains of death.”[177] “And so some of the masters of Taoism, such, for instance, as Chang-Tao-Ling, ascended to heaven without dying, by climbing a lofty peak and vanishing into the skies.”[178] The ordinary Taoists accepted fully the idea of immortality. They “taught the doctrine of purgatory for those who were not evil. To arrive at this, Lao-tseu simply expanded and applied to mankind generally an idea that was already familiar to him, the conception of the transmigration of one soul through several successive bodies. By means of such expiatory transformations, a man who had not reached it directly through the holiness of his life, could attain the immortality of genii and the blessed.”[179]