At the center of the alchemist's quest was the legendary philosopher's stone, a magical piece of the perfect gold, which could immediately transform any substance it touched into gold as pure as its own nature. The Emerald Tablets of the great Hermes Trismegistus spoke of such a marvelous catalyst, and ever since that secret knowledge had been made known to certain individuals, the philosopher's stone had become the symbol of the alchemical pursuit. According to tradition, Albertus Magnus actually came to possess such a wonder of transmutation, and Helvetius was given a small piece of the philosopher's stone by a mysterious man in black.
Some alchemists believed that the stone was somehow hatched like a chick from an egg if one could only find the proper ingredients with which to create the substance of the shell and the "yolk." Others believed that the philosopher's stone, that most marvelous of all catalysts, oozed somehow out of the moon or from one of the stars and fell to Earth where it solidified into the magical stone of transformation.
As the works of more of the alchemists have come to light, it becomes clear that the philosopher's stone wasn't really a stone at all—even though it is always referred to as such. Sometimes the catalyst of transmutation is described as a divine child, an angel, a dragon,
Many alchemists began to consider that somehow the philosopher's stone was not a thing at all, but a system of knowledge. Once the alchemist truly perceived the reality that lay behind the symbols, he would achieve an intellectual and spiritual level wherein he would become one with the power that existed within the mysterious goal for which he searched so long. Once he understood what the philosopher' stone represented, he would have found it at last—and he would have become one with it.
Many scholars have since insisted that the true alchemists sought not to turn base metals into gold, but to transform the dense material of their physical bodies into a spiritually evolved immaterial entity. In this perspective, the philosopher's stone becomes the Holy Spirit that mystically transmutes humans into true manifestations of God on Earth.