The German physician Theophrastus Bombast von Hohenheim traveled throughout Europe, practicing medicine, occultism, and alchemy under the name of Paracelsus. As with so many of the true alchemists, Paracelsus believed that it was far more important to contemplate nature and the majesty of God's handiworks than to spend all one's time studying the knowledge that could be found in books. If one could acquire the kind of purity of belief, such as Jesus (c. 6 B.C.E.–c. 30 C.E.) affirmed existed in the heart of a child, one could literally transform base substances into precious metals and gems, for the primary ingredient necessary for alchemical success lay in obtaining the prima materia, the essence of all substances, the primeval building blocks of the universe. In the view of Paracelsus, this essential substance was both visible and invisible, and it was the soul of the world from which all elements had sprung, and its power was accessible to all who had the purity of heart and the faith to attain it.