Kantian ethics refers to the deontological ethical theory of German philosopher Immanuel Kant. Kant thought that it was possible to develop a consistent moral system by using reason.
Kant taught that there were some moral laws that all rational beings had to obey simply because they were rational beings. Kant argued that the supreme principle of morality is a standard of rationality which he called the Categorical Imperative (CI).
The categorical imperative is objective, rational and unconditional principle that we must follow despite any desire or inclination to violate it. According to him all immoral actions are irrational because they violate Categorical Imperative.