Beweis des Brouwerschen Fixpunktsatzes in zwei Zeilen.

Algebra is the offer made by the devil to the mathematician. The devil says: `I will give you this powerful machine, it will answer any question you like. All you need to do is give me your soul: give up geometry and you will have this marvellous machine.’ (Atiyah)

Mengen, Kategorien, Funktoren – zum formalen Aufbau der modernen Mathematik.