Final answer:
Immanuel Kant's categorical imperative states that an action is moral if it can be universalized without contradiction, meaning it could be a rule for all rational beings. This principle relies on rationality and the capability to reason a priori, representing a shift from faith-based or utilitarian ethics.
Step-by-step explanation:
The Enlightenment philosopher Immanuel Kant established a test for moral permissibility through what he calls the categorical imperative. Kant's universal law test suggests that an action is morally allowable if it can be made into a universal principle that applies to all rational beings. This test is framed by the statement: "Act only according to that maxim whereby you can, at the same time, will that it should become a universal law." In essence, if the reason for your action (the maxim) could be adopted by everyone without contradiction or creating an impossible situation, then the action is moral. For example, if everyone lied, trust would be impossible, thwarting the purpose of lying to achieve a desired end. Therefore, lying fails the universal law test and is deemed immoral.
Kant's view on human reason and morality rests on the idea that our capability to reason sets us apart from animals. He believed that our rationality allows us to derive moral laws a priori, or independently of experience, which guides human conduct and elevates it above mere animal instinct. In this way, Kant argues for a form of ethical conduct that is grounded in rationality and the principle of universalizability, rather than religious faith or utilitarian calculus, which might justify the use of individuals for the majority's benefit.