Kant's Three Critiques Explained 2/3
Critique of Practical Reason: What Should We Do?
Shifting from knowledge to ethics, Kant argues that morality is based on practical reason, which determines universal moral laws. He introduces the categorical imperative, a principle that requires us to act according to moral laws that we would want everyone to follow. True morality, he insists, comes from autonomy—the ability to legislate moral principles for ourselves rather than following external influences. Though Kant argues you can discover right and wrong using only reason and experience, to make sense of moral responsibility, Kant postulates the necessity of freedom, God, and immortality, though he believes that these cannot be known through pure reason alone, because they are outside the realm of observable phenomena.
Immanuel Kant’s moral philosophy is rooted in the idea that ethics must be grounded in reason rather than emotions, consequences, or social conventions. His Critique of Practical Reason was written as a part of a philosophical conversation that was going on throughout Europe at the time.
He rejected David Hume’s claim that morality is based on emotions and sentiment. Moral laws must be objective and universal, derived from rational principles rather than sentiment and feelings. If morality was based on emotions, it would vary from person to person, making it impossible to establish universal moral laws.
Kant also disagreed with the rationalists (Leibniz and Christian Wolff), who attempted to construct morality as a system of logical deductions, much like mathematics. He agreed that morality is grounded in reason, but he rejected their metaphysical approach because he rejected the validity of metaphysics. The rationalists believed you could move from what a thing was (its being) to what a thing was for (it’s ethical use) by means of deductive reasoning. Kant did not believe you could know being. Instead, he argued that moral duties can be reasoned to inductively from the many instances of ethical use and the effect those uses have on society. We don’t need to know the metaphysical nature of a thing (what it is in itself) to employ practical reason and find moral principles. Moral principles are questions, for Kant, of application to real-world decision-making not abstraction from first principles.
One of the most significant influences on Kant was Jean-Jacques Rousseau’s concept of moral autonomy. Rousseau had argued that true morality comes from acting according to self-imposed laws rather than external laws. Kant embraced and expanded on this idea, making it a cornerstone of his ethical system. For him, moral agents are truly free only when they act according to universal moral laws that they rationally recognize and choose for themselves.
Additionally, Kant opposed both virtue ethics and utilitarianism. He rejected Aristotle’s virtue ethics, which focused on cultivating virtues and achieving eudaimonia (human flourishing/happiness), arguing that moral actions should be determined by duty rather than character development. Similarly, he dismissed utilitarianism, which bases morality on the consequences of actions. Instead, Kant insisted that moral actions must be performed out of duty alone, regardless of their outcomes.
At the core of Kant’s ethical system is the Categorical Imperative, which serves as the fundamental principle of moral law. Unlike hypothetical imperatives, which are conditional and dependent on personal desires (e.g., “If you want to be healthy, you should exercise”), the Categorical Imperative is unconditional and applies to all rational beings at all times is equivalent situations. True morality is based on duty and reason, not emotions or consequences.
Key Features of the Categorical Imperative
Moral laws must be universal – If an action is morally right, it must be right for everyone in all similar circumstances.
Morality is based on duty, not consequences – Kant argued that an action is right if it follows a rational moral law, regardless of its consequences.
Humans must be treated as ends, not means – People should never be used as mere tools for someone else’s benefit but must be respected as autonomous moral agents.
Kant formulated the Categorical Imperative in three different ways, each providing a different perspective on the same fundamental moral principle:
1. The Formula of Universal Law
“Act only according to that maxim whereby you can at the same time will that it should become a universal law.”
The relevant moral question would be: Would this action lead to a desirable world if everyone in the world acted the same way in a similar situation? If the action would lead to a contradiction or an undesirable world, it is morally wrong. If everyone acting this way
Example: Lying is immoral because if everyone lied, trust would collapse, making truthful communication impossible.
2. The Formula of Humanity
“Act in such a way that you treat humanity, whether in your own person or in the person of any other, always at the same time as an end, never merely as a means.”
People should never be exploited, manipulated, or used as mere instruments for someone else’s goals.
Example: Befriending someone solely to borrow money and then discarding the friendship once the loan is received would be immoral because it treats the person as a means rather than valuing them as an individual.
3. The Formula of the Kingdom of Ends
“Act according to maxims of a universally legislating member of a merely possible kingdom of ends.”
This means that one should behave as if they are contributing to a society where everyone follows rational moral rules. In such a world, moral laws are created based on rational deliberation, and each person is treated as an autonomous, self-legislating individual.
Example: When designing ethical rules for an ideal society, one should ask: Would my actions be acceptable if they were the basis for universal law? If the answer is no, then the action is immoral.
Kant’s moral philosophy, though consistently discussed, is rarely embraced as an ethical theories. By grounding morality in rationality and duty, he provided a framework for ethical decision-making that attempted to retain a traditional ethic without the traditional metaphysic. What has been influential is the assumption that the seat of ethics is the experience of the individual rather than metaphysical definitions. Modern debates in ethics, law, and human rights generally move from life examples to laws, arguing ethical positions inductively. Metaphysics and ethics have been effectively severed. Also, Kant’s insistence that humans must be treated as ends in themselves has also had a profound impact on human rights philosophy, shaping the legal and ethical conversation. Previously it was believed that only God could be treated as an end in and of himself.
Next we will look at Kant’s Critique of Judgement.
For Kant, is rationality always moral? He sees freedom as the ability to choose a morality based on some hypothetical universal concept. Is Kant simultaneously denying metaphysics and encouraging his own pseudo-metaphysic? Why does philosophy tend towards an optimistic view of man's efforts and achievements?