Immanuel Kant-Fundamental Principles of the Metaphysics of Morals. The categorical imperative, of accepting a rule for oneself only if one accepts it for all others and vice versa is only rational as such rules are reciprocated. Even if a rule is rational, if nobody else follows it and you do then you are in that situation being irrational. Equality has to be among equals in some capacity. Moral rules have to be constrained by real world conditions since these are what make rules universalizable: it isn’t as if truth is divorced from the material world. Insofar as one is rational and deals with rational people then categorical imperatives should kick in. But these imperatives serve as restraints on means in the pursuit of ends by individuals and not as ends in themselves.
