In 1800 Schelling published "System des transcendentalen Idealismus" ("System of Transcendental Idealism"). In this book Schelling described transcendental philosophy and nature philosophy as complementary to one another. Fichte reacted by stating that Schelling's argument was unsound: in Fichte's theory nature as Not-Self ("Nicht-Ich" = object) could not be a subject of philosophy, whose essential content is the subjective activity of the human intellect. The breach became unrecoverable in 1801 after Schelling published "Darstellung des Systems meiner Philosophie" ("Presentation of My System of Philosophy"). Fichte thought this title absurd since, in his opinion, philosophy could not be personalized. Moreover, in this book Schelling publicly expressed his estimation of Spinoza, whose work Fichte had repudiated as dogmatism, and declared that nature and spirit differ only in their quantity, but are essentially identical. According to Schelling, the absolute was the indifference to identity, which he considered to be an essential philosophical subject.