Kant's Categorical imperative.

The constant dilemma that Kant is dealing with in Grounding for the Metaphysics of Morals is attempting to find a rational foundation or connection between all moral conduct. Kant believed that there was an absolute moral law that carried with it a universal validity. It is through his categorical imperative that he attempts to discover and understand this a priori law. Kant effectively shows us where and when his categorical imperative can be successfully, as …

…would be applicable to the real world is another question. The categorical imperative as it is, would work perfectly in the kingdom of ends. It could not be expected to work in real societies, though. It is not plausible based on the reality of human nature. Man does not treat others as equals (let alone as ends within themselves), and more often than not is indifferent to most things that do not directly affect him.