in late 1854 to the work of the philosopher Arthur Schopenhauer. The composer was immediately struck by the philosophical ideas to be found in The World as Will and Representation (Die Welt als Wille und Vorstellung), and the similarities between the two men's world-views became clear. Man, according to Schopenhauer, is driven by continued, unachievable desires, and the gulf between our desires and the possibility of achieving them leads to misery while the world is a representation of an unknowable reality. Our representation of the world is Phenomenon, while the unknowable reality is Noumenon: concepts originally posited by Kant. Schopenhauer's influence on Tristan und Isolde is most evident in the second and third acts. The second act, in which the lovers meet, and the third act, during which Tristan longs for release from the passions that torment him, have often proved puzzling to opera-goers unfamiliar with Schopenhauer's work. Wagner uses the metaphor of Day and Night in the second act to designate the realms inhabited by Tristan and Isolde. The world of Day is one in which the lovers are bound by the dictates of King Marke's court and in which the lovers must smother their mutual love and pretend as if they do not care for each other: it is a realm of falsehood and unreality. Under the dictates of the realm of Day, Tristan was forced to remove Isolde from Ireland and to marry her to his Uncle Marke – actions against Tristan's secret desires. The realm of Night, in contrast, is the representation of intrinsic reality, in which the lovers can be together and their desires can be openly expressed and reach fulfilment: it is the realm of oneness, truth and reality and can only be achieved fully upon the deaths of the lovers. The realm of Night, therefore, becomes also the realm of death: the only world in which Tristan and Isolde can be as one forever, and it is this realm that Tristan speaks of at the end of Act II ("Dem Land das Tristan meint, der Sonne Licht nicht scheint"). In Act III, Tristan rages against the daylight and frequently cries out for release from his desires (Sehnen). In this way, Wagner implicitly equates the realm of Day with Schopenhauer's concept of Phenomenon and the realm of Night with Schopenhauer's concept of Noumenon. While none of this is explicitly stated in the libretto, Tristan's