The Birth of Tragedy was Nietzsche's first philosophical work. He is thus determined in his forward to establish himself as someone with something serious to say about the German character and its relationship to the Greeks. As a young philosopher, Nietzsche takes the clever step of associating himself with Wagner, the great German composer of his day. By enlisting him as his ally, Nietzsche ensures that he will not be written off so easily as some starry-eyed student of aesthetics. He implies that if Wagner agrees with him that art is the highest task of life, then his readers should agree with him as well.

While Nietzsche ostensibly writes his forward for Wagner, it is clear that he writes it with the general public in mind. He suggests that serious readers, whom he calls "those earnest ones," will understand that questions of aesthetics are of the highest importance. By suggesting that anyone who does not take his work seriously is missing the point, Nietzsche plays off of the intellectual insecurities of his readers and gains their attention and respect.

From the beginning of his essay, Nietzsche makes it clear that he will be discussing aesthetics on his own terms. He creates a new frame of reference for his readers to understand art and the artistic process, that is, the dualistic opposition between Apollo and Dionysus. He thus lays the groundwork for discussing various affected states that are relevant to the artistic process, all of which relate to either Apollo or Dionysus. In doing so, he creates numerous oppositions that would not be logically apparent outside of his structure; for example, we do not ordinarily think of dreaming and drunkenness as being opposite states. But, under Nietzsche's program, they fall under the influence of Apollo and Dionysus respectively, and thus represent opposite energies.

After naming Apollo and Dionysus as the two opposing elements around which his argument (and art in general) revolves, Nietzsche proceeds with "duality" as his main metaphor for the artistic process. Apollo and Dionysus are merely the symbols of this duality, which, in this chapter, he elucidates in terms of dreams and drunkenness. For Nietzsche, dreams represent the realm of beautiful forms and symbols, an orderly place of light and appearance. Drunkenness, on the other hand, is that state of wild passions where the boundaries between "self" and "other" dissolve.

In his discussion of dreams, Nietzsche introduces terms that will reappear throughout the essay, such as "appearance" and "the apprehension of form." The idea of appearance is related to Plato's cave, to which Nietzsche makes reference when he writes that the dreamer sees life pass before him, "not like mere shadows on the wall—for in these scenes he lives and suffers—and yet not without that fleeting sensation of appearance." One has life-like experiences in ones dreams, but is still aware that these experiences are mere appearances and that the reality lies beneath. Nietzsche makes the assumption here that, when dreaming, one is always aware that one is dreaming; those who are entirely caught up in their dreams are not experiencing Apollonian beauty, but rather Dionysian ecstasy.

Whereas Apollo represents the state of "measured restraint," in which man remains separate from the emotions and illusions that buffet him, Dionysus represents the breakdown of those walls. From the progression of Nietzsche's analysis, we see that he does not view the Apollonian and the Dionysian realms equally, but rather sees the latter as the negation of the former. Dionysus enters the field when reason fails, not the other way around.

This is not to say that Nietzsche derides the Dionysian state; on the contrary, he sees it as fundamental to the creation of art. He gives the example of the singing and dancing crowds of the Germanic Middle Ages, who whirled in ecstatic celebration of St. John and St. Vitus. To those who would condemn this behavior as a symptom of "folk-diseases," he writes, "Such poor wretches can not imagine how anemic and ghastly their so-called 'healthy-mindedness' seems in contrast to the glowing life of the Dionysian revelers rushing past them." One must submit to Dionysian madness in order to attain the state of primordial unity, a state beyond social barriers and narrow thinking.

Friedrich Nietzsche’s concept of the Dionysian, which he refines and alters over the course of his career, stands as a pointed counterbalance to the thoroughgoing rationality that is so prominent in most philosophy. In most scholarly investigations, the importance of truth and knowledge are taken as givens, and thinkers trouble themselves only over questions of how best to achieve truth and knowledge. By contrast, Nietzsche questions where this drive for truth and knowledge come from and answers that they are products of a particular, Socratic view of the world. Deeper than this impulse for truth is the Dionysian impulse to give free rein to the passions and to lose oneself in ecstatic frenzy.

We cannot properly appreciate or criticize the Dionysian from within a tradition of rationality because the Dionysian stands outside rationality. As much as the civilized world may wish to deny it, the Dionysian is the source of our myths, our passions, and our instincts, none of which are bounded by reason. While the civilizing force of the Apollonian is an essential counterbalance—contrary to some stereotypes of Nietzsche, he is firmly against the complete abandonment of reason and civilization—Nietzsche warns that we lose the deepest and richest aspects of our nature if we reject the Dionysian forces within us.

For Nietzsche, art is not just a form of human activity but is rather the highest expression of the human spirit. The thrust of The Birth of Tragedy is well expressed in what is perhaps its most famous line, near the end of Chapter 5: “it is only as an aesthetic phenomenon that existence and the world are eternally justified.” One of Nietzsche’s concerns in The Birth of Tragedy is to address the question of the best stance to take toward existence and the world. He criticizes his own age (though his words apply equally to the present day) for being overly rationalistic, for assuming that it is best to treat existence and the world primarily as objects of knowledge. For Nietzsche, this stance makes life meaningless because knowledge and rationality in themselves do nothing to justify existence and the world.

Life finds meaning, according to Nietzsche, only through art. Art, music, and tragedy in particular bring us to a deeper level of experience than philosophy and rationality. Existence and the world become meaningful not as objects of knowledge but as artistic experiences. According to Nietzsche, art does not find a role in the larger context of life, but rather life takes on meaning and significance only as it is expressed in art.

By attacking Socrates, Nietzsche effectively attacks the entire tradition of Western philosophy. While a significant group of Greek philosophers predate Socrates, philosophy generally identifies its start as a distinctive discipline in Socrates’ method of doubt, dialogue, and rational inquiry. While Nietzsche acknowledges that Socrates gave birth to a new and distinctive tradition, he is more interested in the tradition that Socrates managed to replace. Greek tragedy as Nietzsche understands it cannot coexist in a world of Socratic rationality. Tragedy gains its strength from exposing the depths that lie beneath our rational surface, whereas Socrates insists that we become fully human only by becoming fully rational.

From Socrates onward, philosophy has been the pursuit of wisdom by rational methods. In suggesting that rational methods cannot reach to the depths of human experience, Nietzsche suggests that philosophy is a shallow pursuit. True wisdom is not the kind that can be processed by the thinking mind, according to Nietzsche. We find true wisdom in the Dionysian dissolution of the self that we find in tragedy, myth, and music.

Nietzsche wrote The Birth of Tragedy at a time when he was most heavily under Wagner’s influence. Nietzsche had met Wagner as a young man and was deeply honored when Wagner chose to befriend him. Wagner impressed his own views on life and art on Nietzsche, and The Birth of Tragedy is, in many ways, a philosophical justification for the work Wagner was carrying out in his operas.

Over the course of the 1870s, however, Nietzsche became increasingly disillusioned with Wagner, and his mature works, starting with Human, All-Too-Human, show Nietzsche finding his own distinctive voice, free from Wagner’s influence. In particular, Nietzsche became disgusted with Wagner’s shallow pro-German nationalism and his anti-Semitism. In contrast to Nietzsche’s later biting attacks on nationalism, The Birth of Tragedy bears Wagner’s influence in its pride in German culture and its hope that a purified German culture can rescue European civilization from the deadening influence of Socratic rationalism.