In Goran Stanivukovic's article on the importance of humanism within The Tempest he points out many instances that indicate that the weight of the play is not on the colonial or the imperial but rather on the individual. Particularly interesting to me was the idea that the power wielded by Prospero came to him through the humanistic education that he received himself, and that the influence that he has over Miranda and Ferdinand has much more to do with his humanist ideals than his brute magical force.
Interestingly, Stanivukovic views Prospero's humanism as a negative influence in the beginning of the play, pointing out how his secret studies cause him to be "enraptured, transported, and fascinated by one sort of power so that he does not care for, and loses secular power" (96). However, I find the very idea that he would gain the magical powers that he does gain from a secular source as a sign of humanism's victories. Rather than resorting to some kind of angelic or devilish source for his powers, he instead studies the classical authors and ideas that are so prevalent in humanism. This is a demonstration that man can be powerful without the crutch of religion, whether in a positive or negative light. Although Prospero initially loses his kingdom because of his studies, those very studies are what allows him to eventually dominate his island and return to power as a wiser ruler, perhaps indicating that humanism, although new and unaccepted by many, will bring wiser rulers to those nations that embrace it.
This source of power can be traced back to particular humanist scholars and philosophers. Tiffany Grace mentions (in an article critiquing Stanivukovic's article) that the idea of "the relevance to Prospero's powers of Pico della Mirandola's distinction between demonic and natural magic" (71) is a topic long discussed by multiple scholars. Pico della Mirandola suggests that magic is a sort of power that allows humans to determine for themselves their path rather than trusting their lives to the will and might of an all-powerful God. His idea that God should not and does not interfere directly with the lives of men is a very humanist idea, a sort of beginning of Deism.
Although there are multiple points throughout the play that emphasize humanism, I think that the concept of humanism as a source of might rather than religious affinity or God is an especially important point to consider in this context. After all, if Prospero had no magical might, there would have been no Tempest at all.
Stanivukovic, Goran. "The Tempest and the Discontents of Humanism." Philogical Quarterly 85.1 (2006): 91-114.
Tiffany, Grace. "The Tempest and humanism." Shakespeare Newsletter Fall 2008: 71. Literature Resource Center. Web. 28 Sept. 2015.