“What is the explanation of all plurality, of all numerical diversity of existence? Time and Space. Indeed it is only through the latter that the former is possible: because the concept “many” inevitably connotes the idea either of succession (time) or of relative position (space).

– Arthur Schopenhauer, On the Basis of Ethics

Time and Space itself imposes plurality upon existence or experience. Schopenhauer uses this premise along with Kant’s Transcendental Aesthetics to argue for the metaphysical unity of life, which in turn acts as foundation for Schopenhauer’s ethics.