This paper considers the foundation of self-realization and the sense of morality that could justify Arne Naess’s claim ‘Self-realization is morally neutral,’ by focusing on the recent debate among deep ecologists. Self-realization, the ultimate norm of Naess’s ecosophy T, is the realization of the maxim ‘everything is interrelated.’ This norm seems to be based on two basic principles: the diminishing of narrow ego, and the integrity between the human and non-human worlds. The paper argues that the former is an extension of Plato’s idea of self-development or self-mastery while the latter is implicit in Aristotle’s holism. It defends that Self-realization is morally neutral only if the term ‘moral’ is considered in the Kantian sense. However, Naess reluctantly distinguishes between ethics and morality, which makes his approach less credible. The paper concludes that Aristotle’s notion of eudaimonia supports Self-realization to qualify as a virtue.