1901 saw the posthumous publication of a work by the German philosopher Friedrich Nietzsche (1844-1900) entitled Der Wille zur Macht, or The Will to Power.
According to The Johns Hopkins Guide to Literary Theory and Criticism, Nietzsche's earlier pronouncement (1887) that "God is dead" means "that faith in God, which involves a total commitment to truthfulness, finally has led to the gradually emerging realization that God does not exist after all and that therefore there can be no objective, absolute values."
Without these absolute values to fall back upon for the justification of any belief or action, each honest person must follow the path selected by his or her own natural internal will: I believe this or do that because I feel the necessityand have the will to do so. The JHG quotes Nietzsche: "One seeks a picture of the world in that philosophy in which we feel freest, i.e. in which our most powerful drive feels free to function."
Grendel's reflection that "The will to power resides among the stalactites of the heart" (128) comes as he considers the death of religion, that the priests themselves no longer believe in the presence of their gods. The weak go through the motions of worship, but the strong have no time for it.
By placing the phrase "will to power" in Grendel's mouth, is Gardner calling a reader to accept the monster's insight as the author's own understanding of the state of contemporary religion? Or is he identifying the Nietzschean philosophy as one which serves to advance The Destroyer's progress through our own time? Or is he simply observing that this is the way things are?