Throughout The Gay Science, Nietzsche treats the concept of egoism as a major theme. Nietzsche proposes egoism as the root of consciousness, which evolves from humanity’s selfish need to preserve the species. According to Nietzsche, both the ancient Greeks and, later, the Christians limited their egoism by belief in divinity. They wrongly believed themselves flawed. Over time, the problem of survival became less of an uncertainty, and the problem shifted to what is the most ideal way to survive. This answer is different for each individual, Nietzsche explains, and depends on one’s instincts; that is, it depends on their identity, which is egoism.Religion lost its authority among individuals who possessed a selfish need to relieve their own suffering.

Nietzsche believes ego drives the quest for all new knowledge:

The inventing of Gods, heroes, and supermen of all kinds, as well as coordinate men and undermen–dwarfs, fairies, centaurs, satyrs, demons, devils–was the inestimable preliminary to the justification of the selfishness and sovereignty of the individual: the freedom which was granted to one God in respect to other Gods, was at last given to the individual himself in respect to laws, customs and neighbors (97).

Nietzsche here explains how the authority of the gods shifted into the hands of those individuals fearless and courageous enough to trust their own instincts towards fulfillment and happiness and eschew herd mentality and moral conventions, which are weighed down by self-doubt.