How does Either/Or contrast aesthetic and ethical ways of living?

In Either/Or, Søren Kierkegaard distinguishes between the aesthetic and ethical spheres of existence, which represent fundamental, competing projects for how to live.1

The Aesthetic Way of Living

The aesthetic stage is characterized by a pursuit of the arts and the erotic, driven by a desire to avoid boredom, which the aesthete views as the root of all evil. Aesthetes define success through premoral criteria, remaining unconcerned with traditional notions of good and evil. Kierkegaard portrays this mode of existence as a fragmented life; the aesthete fails to form a cohesive identity, becoming a mere "bundle of events" without an inner core.1

The Ethical Way of Living

The ethical stage, represented by the character Judge William, introduces the necessity of commitment and temporal continuity. Unlike the aesthetic life, the ethical life is defined by moral responsibility and the formation of a stable self. Judge William argues that the ethical does not abolish the aesthetic but rather ennobles it; for instance, through the commitment of marriage, the sensuous is transformed and integrated into a life of purpose. While the aesthetic is concerned with the immediate, the ethical provides the structure and identity required to become a true self.1