Here, with the exeption of a short stay at Mannheim, he spent the rest of his life. For Schopenhauer Kant's distinction between the phenomenal and noumenal opened new views into foundations ot ethics, the nature of art and music, the true nature of religion - he was explicitly atheist, the first great philosopher of the West to be so. He argued that noumenal and phenomenal are the same thing understood in different ways. According to Schopenhauer, the will is the ultimate source of reality, which is essentially irrational. The will in itself is timeless and imperishable.
Nature is indifference to the individual, the species is favored over the individual.
The universe before there was any life was nothing but embodiment of will - there is as much will in a pool of water or dead star as in a human being or human action. The will to exist is not itself this noumenal will but a manifestation of it in the world of phenomena. Just as the spraying drops of the roaring waterfall change with lightning rapidly, while the rainbow which they sustain remains immovably at rest, quote untouched by that restless change, so every Idea, i.e. every species of living beings remains entirely untouched by the constant changes of its individuals. There is no hope of things becoming better, life itself is painful, manifested in the aimlessness and dissatisfaction. Man must understand that all willing is in vain.