In the desert of science. – To the man of science on his unassuming and laborious travels, which must often enough be journeys through the desert, there appear those glittering mirages called ‘philosophical systems’: with bewitching, deceptive power they show the solution of all enigmas and the freshest draught of the true water of life to be near at hand; his heart rejoices, and it seems to the weary traveller that his lips already touch the goal of all the perseverance and sorrows of the scientific life, so that he involuntarily presses forward.