Deontological ethics is the school of thought in philosophy that judges an action's goodness based not on its consequences but on its adherence to a set of rules or duties. Other ethical theories like utilitarianism and ethical egoism have advocated judging an action's ethical standing based upon its consequences. In contrast, deontology is often called duty ethics or nonconsequentialist ethics.
Immanuel Kant's categorical imperative is perhaps the most significant and important idea in deontology. The two critical elements to the categorical imperative are: