The Metaphysics of Morals by Immanuel Kant Chapter 2 Page 6

friendship required of every man, because, prior to all experience, this duty is involved as duty in the idea of a reason determining the will by a priori principles.

When we add further that, unless we deny that the notion of morality has any truth or reference to any possible object, we must admit that its law must be valid, not merely for men but for all rational creatures generally, not merely under certain contingent conditions or with exceptions but with absolute necessity, then it is clear that no experience could enable us to infer even the possibility of such apodeictic laws. For with what right could we bring into unbounded respect as a universal precept for every rational nature that which perhaps holds only under the contingent conditions of humanity?

Or how could laws of the