Schopenhauer's thought exerted remarkable influence on the last generation of German romantics. Wagner assimilated his theory into his musical production and Niestsche, who would later attack him, was also inspired by him in his early writings. It can be said, in general terms, that Schopenhauer initiates the vitalist and irrationalist currents that would appear later.
Schopenhauer modifies the phenomenon-number distinction: the 'phenomenon' is a 'representation' but not in the Kantian sense, it is considered an illusion or dream (the veil of 'Maya' according to the conception of Indian philosophy.)
What is hidden behind is the infinite and blind 'will', that is, irrational. Schopenhauer, who knew deeply the philosophy of India, reinterprets it from a romantic and pessimistic perspective.
In contrast to Hegel, Schopenhauer will not see in reality the manifestation of reason but that of an infinite blind outside which gradually multiplies in the individuals of the illusory world of representation (space and time are the 'principle of individuation') of how images on the faces of a crystal would multiply - Yeah. But that will is always misery and pain as a result of an ever dissatisfied desire. For this reason it is that man, as he is conscious individuation of this infinite will, is destined to suffer. Every positive feeling, even pleasure, is the absence of pain. There is no liberation but the annulment of the volutad to live and of the self.
Art, particularly tragedy and music, provide a first liberation since it nullifies the self and merges it with the universal will, in collective eternal pain. But true liberation is what is achieved by the path of ethics (ethics of compassion, joining the pain of others) and the asceticism of Buddhist inspiration (nirvana) that involves nullifying oneself to merge with cosmic unity.