Kantian Duty Based (Deontological) Ethics


The term deontology comes from the Greek word deon, meaning duty. The theory of deontology states we are morally obligated to act in accordance with a certain set of principles and rules regardless of outcome. In religious deontology, the principles derive from divine commandment so that under religious laws, we are morally obligated not to steal, lie, or cheat. Thus, deontological theories and duties have existed for many centuries. Immanuel Kant, the theory’s celebrated proponent, formulated the most influential form of a secular deontological moral theory in 1788. Unlike religious deontological theories, the rules (or maxims) in Kant’s deontological theory derive from human reason.

To better understand deontology, compare it to some opposing theories, such as utilitarianism, which says we have an obligation to take the course of action that achieves the most positive outcome or consequence. According the theory of utility, the best consequence is happiness/pleasure, because it is considered the absolute good. Consequentialism tells us we need to take into account the final consequence of our action, even if the act itself is not morally good.

Immanuel Kant

Immanuel Kant was born in 1724 in the Prussian city of Königsberg. He essentially spent his whole adult life at the university and never truly travelled outside of the city. He only stopped working at the university three years before his death. He was a philosopher and scientist specializing in many areas, including mathematics, astrophysics, geography and anthropology. He wrote several dense, difficult-to-read but highly influential texts regarding metaphysics, metaethics and practical morality, science, history and politics. He was the first recorded scholar to suggest that some of the faint nebulae visible with a telescope are actually separate universes in the sky.

As with many scholars of his time, Kant’s new ideas and published works about the nature of reality and free will were widely condemned, but they have remained prominently influential to this day. In terms of ethics, the most significant of his works are Groundwork in the Metaphysics of Morals (1785), Critique of Practical Reason (1788), and Metaphysics of Morals (1798). These texts constitute the foundation of Kant’s own moral philosophy.

A Theory of Duty

Some terminology to consider:

Moral agent: An agent is a person who performs an action; a moral agent is a person with the capacity to act morally.

Maxim: rule or principle

Will: the faculty of deciding, choosing, or acting

Deontological theories differ from utilitarian theories in several key ways. The most notable difference is utilitarianism aims at a goal of greatest happiness (or the best consequence) and justifies any act that achieves that goal. Deontological theories hold that some acts are always wrong, even if the act leads to an admirable outcome. Actions in deontology are always judged independently of their outcome. An act can be morally bad but may unintentionally lead to a favorable outcome.

Kant is responsible for the most prominent and well-known form of deontological ethics. Kant’s moral theory is based on his view of the human being as having the unique capacity for rationality. No other animal possesses such a propensity for reasoned thought and action, and it is exactly this ability that requires human beings to act in accordance with and for the sake of moral law or duty. Kant believes human inclinations, emotions and consequences should play no role in moral action; therefore, the motivation behind an action must be based on obligation and well thought out before the action takes place. Morality should, in theory, provide people with a framework of rational rules that guide and prevent certain actions and are independent of personal intentions and desires.

According to Kant, the moral worth of an action is determined by the human will, which is the only thing in the world that can be considered good without qualification. Good will is exercised by acting according to moral duty/law. Moral law consists of a set of maxims, which are categorical in nature – we are bound by duty to act in accordance with categorical imperatives.

Categorical Imperatives

There are three formulations of Kant’s categorical imperative.

The First Formulation of the Imperative

“Act only according to that maxim whereby you can at the same time will that it should become a universal law without contradiction.” – Immanuel Kant, Groundwork of Metaphysic of Morals

Kant states that a true moral proposition must not be tied to any particular conditions, including the identity of the person making the decision. A moral maxim must be disconnected from the particular physical details surrounding its proposition and should be applicable to any rational being. According to Kant, we first have a perfect duty not to act by maxims that result in logical contradictions.

Second, we have imperfect duties, which are still based on pure reason but allow for interpretation regarding how they are performed. Because these duties depend loosely on the subjective preferences of mankind, they are not as strong as perfect duties but are still morally binding. Unlike perfect duties, people do not attract blame if they do not complete an imperfect duty, but they receive praise if they complete it, for they have gone beyond basic duty and taken responsibility upon themselves. Imperfect duties are circumstantial, meaning that one can not reasonably exist in a constant state of performing that duty. What differentiates perfect and imperfect duties is that imperfect duties are never truly completed.

The first formulation of the categorical imperative appears similar to the Golden Rule: “Do not impose on others what you do not wish for yourself.” Kant’s first categorical imperative sounds like a paraphrase of the Golden Rule. However, the Golden Rule is neither purely formal nor universally binding. It is empirical in the sense that applying it requires context; for example, if you don’t want others to hit you, then don’t hit them. Also, it is a hypothetical imperative in the sense that it can be formulated, and its “if-then” relationship is open for dispute.

The Second Formulation of the Imperative

“Act in such a way that you treat humanity, whether in your own person or in the person of any other, never merely as a means to an end but always at the same time as an end.” – Immanuel Kant, Groundwork of Metaphysic of Morals

This imperative states that every rational action must be considered not only a principle, but also an end. Most ends are subjective in nature because they need only be pursued if they are in line with a hypothetical imperative. (A hypothetical imperative is a demand of reason that is conditional. It tells us how to act to achieve a specific goal e.g. I must drink when I need to slake my thirst.)

For an end to be objective, it would need to be pursued categorically. The free will is the source of all rational action. Because the autonomous will is the one and only source of moral action, it contradicts the first formulation of the categorical imperative to claim that a person is merely a means to some other end instead of an end in him or herself.

Based on this, Kant derives the second formulation from the first. A person has a perfect duty not to use themselves or others merely as a means to some other end. For example, someone who owns slaves would be asserting a moral right to own a slave by asserting their rights over another person. However, this reasoning violates the categorical imperative because it denies the basis for free rational action and disregards the person as an end in themselves. In Kantian ethics, one cannot treat another person as a means to an end. Under the second formulation of the categorical imperative, a person must maintain her moral duty to seek an end that is equal for all people.

The Third Formulation of the Imperative

“Therefore, every rational being must so act as if he were through his maxim always a legislating member in the universal kingdom of ends.” – Immanuel Kant, Groundwork of Metaphysic of Morals

A truly autonomous will is not subjugated to any interest; it is subject to those laws it makes for itself, but the will must also regard those laws as if others are bound by the laws. If the laws are not universal, they are not laws of conduct at all. Kant suggests that people treat themselves and others always as ends and never merely as means. People ought to act only by maxims that harmonize with a possible kingdom of ends. We have a perfect duty not to act by maxims that create incoherent or impossible states of natural affairs when we attempt to universalize them, and we have an imperfect duty not to act by maxims that lead to unstable or greatly undesirable states of affairs for all parties involved.

Using reasoned judgment we can apply this formula to any maxim and discover whether it is morally permissible under deontological ethics. Let’s take, for example, the act of picking flowers from the local park. The flowers are very pretty, and one may want to take some home. Essentially, this requires adopting a maxim that supports doing whatever one wants to do. Using the formula of the universal law (categorical imperative), there are a few irrationalities and contradictions that arise from the adoption of such a maxim as law.  If everyone were to do this, there would be no flowers left in the park, and the act contradicts the original motive for picking the flowers. The better option is to go to a shop and order or plant one’s own flowers.

There are a few acts that are always forbidden, such as lying, which negatively affects trust between people and the meaning of truth. This rule remains the case even when lying has advantageous or even morally admirable consequences. Imagine a psychotic criminal wants to kill your colleague, who fired the psychotic. If you lie about the whereabouts of your colleague, then an innocent life will be saved. It seems moral duty forbids you from lying. However, a higher moral duty trumps the duty not to lie. That is, the obligation not to kill or help others in killing, is a higher moral duty that we should follow.

Alternative Formulation of Categorical Imperative

Kant expressed the categorical imperative in a few different ways. The most important of these is the formula of humanity: “Act in such a way that you treat humanity, whether in your own person or in the person of another, always at the same time as an end and never simply as a means.”

This is a personal perspective on the same moral theory. To fail to do this would be to treat others in a way that contradicts the moral law. For example, if I steal a book from a friend, I am treating him as a means only (to obtain a book). If I ask to have his book, I am respecting his right to say no and am thereby treating him as an end in himself, not as a means to an end. If I only ask for the book in order to appear nice and hope that my friend is likely to do more things for me in the future, then I am still treating him as a means only. It is true that everyone uses people as a means to an end. Bus/taxi-drivers get us where we want to go; factory workers are the means to producing objects and ultimately profit for their employer. But using people only to get what we want and consistently disrespecting their human worth is against moral law. An example of this would be a factory owner providing unsafe working conditions, such as Foxconn in China or factories in countries that impose inhumane working conditions and pay less than minimum wage.


One of the biggest criticisms of Kantian ethics is that it discounts outcome as a valid factor in evaluating the morality of an action. While it is not necessarily wise to rely solely on outcome (as in utilitarianism/consequentialism), it is not a good idea to completely ignore the outcome altogether. Based on Kant’s formula of humanity, human life is sacred and inviolable, meaning one cannot enslave a few people even if it would enable more people to lead better lives. Killing one person to save the lives of millions is impermissible in Kantian ethics.

At times Kantian moral duty seems to contradict our natural inclinations and common sense. If we obey the moral law rather than our intuitions, we are acting morally. Deontological ethics is weaker when it comes to informing us how to live well or developing virtues of character.


By: Ali Shakil




  1. Kant, Immanuel. 1785. “First Section: Transition from the Common Rational Knowledge of Morals to the Philosophical”, Groundwork of the Metaphysic of Morals.