He was then reflecting on the problems of naturalistic philosophy. Spencer's system had just come into vogue. Friedrich Nietzsche despised this cosmogony which affected to supplant Christianity and yet remained in submission to it. Spencer ignored Providence, yet believed in progress. He preached the reality of a concert between the movements of things and the aspirations of humanity. He preserved the Christian harmonies in a God-less universe. Friedrich Nietzsche had been a pupil at more virile schools; he heard Empedocles, Heraclitus, Spinoza, Goethe, thinkers who with a calm regard could study Nature without seeking in her some assent to their longings. He remained obedient to these masters, and he felt growing and ripening in him a great and a new idea. We can divine from his letters the emotion with which he was seized. He needed to be alone, and energetically defended his solitude. Paul Rée, who admired _The Dawn,_ wished to go to him and tell him so. Friedrich Nietzsche learnt this and was in despair. "MY GOOD LISBETH," he wrote to his sister, "I cannot make up my mind to telegraph to Rée not to come. Nevertheless, I must consider him an enemy who comes to interrupt my summer's work, my work in the Engadine, that is to say my duty itself, my 'one thing necessary.' A man here, in the middle of all these thoughts which gush out from all sides within me--it would be a terrible thing; and if I cannot defend my solitude better, I leave Europe for many years, I swear it! I have no more time to lose." Fräulein Nietzsche forewarned Paul Rée, who abandoned his project.