Aristotelian vs. Kantian Ethics: Contrasting Approaches to Morality

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Aristotle’s ethics is teleological, material, post, and heteronomous. By contrast, Kantian ethics is formal, a priori, and independent. According to Aristotle, the highest good of man and his purpose or goal is to live well, or happiness (eudaimonia in Greek). We all agree that we want to be happy and try to direct our behavior to achieve it. Aristotle bases happiness on his teleological conception of nature, where all beings have a goal or purpose. While material things may bring pleasure, true happiness, according to Aristotle, is living a life guided by reason and the search for truth, ultimately living a life worthy of our rational nature. The greatest happiness is a contemplative life, but not everyone can achieve it. Desires are important because they motivate action, leading Aristotle to describe human action as a “deliberate desire” exercised from a “desiring intelligence.” A good person acts in accordance with their natural tendencies and desires, but also knows, educates, and sorts them. This requires a hierarchy among desires and preferences. Thus, high moral virtue is phronesis or prudential reason, enabling man to achieve happiness deliberately.

Kant radically innovated ethics by defending deontology against Aristotle’s teleologism. For Kant, the good is discharging one’s duty. The moral criterion is not found externally in the pursuit of happiness but internally, in one’s moral conscience. Kant sought to overcome the moral relativism of material ethics, like Aristotle’s, where differing views of the good could lead to conflicts. He aimed to lay the foundations for a universal ethical system. Kant formulates his categorical imperative: “Act only according to that maxim whereby you can at the same time will that it should become a universal law.” Unlike Aristotle, Kant believes desires and motivations should be subject to reason and duty.

The legacy of Aristotle includes Thomism and Utilitarianism. After Aristotle, the concern for happiness as central to ethics continued in Stoicism and Epicureanism. It would be in medieval theology and morality, specifically Thomism, where this concern would be prominent. In this tradition, the human will is attracted to the good, and human intelligence establishes an order to achieve man’s true purpose. As humans are children of God, man’s happiness lies in the contemplation of God, the highest good.

Utilitarianism also revisits the Aristotelian ideal of happiness, but as a variant of hedonism, emphasizing pleasure. It also considers social feelings as motives for human behavior. Immanuel Kant criticizes the Aristotelian tradition, arguing that the pursuit of happiness often conflicts with fulfilling our duties. To the question, “How do I act morally?” Kant’s answer is not about happiness or utility, but about being worthy and deserving of happiness, achieved through compliance with duty. Kantian ethics is formal, providing a universal and timeless categorical imperative.

Material vs. Formal Ethics

Material ethical theories differ in establishing what is morally good. They vary in their understanding of purpose and reason, leading to ethical relativism. In contrast, formal or duty-based ethics, championed by Immanuel Kant, argue that human behavior should be driven not by an end or supreme good, but by conscience and rational duty. Kant sought to overcome ethical relativism by establishing a universal moral standard. He believed reason could not define happiness universally, as everyone understands it differently. His approach was formal, focusing on the intention behind actions. These are also called ethics of duty, as they claim that moral behavior should be guided solely by duty, doing what is right because it is imposed on one’s conscience, expecting nothing in return. Ethics in this tradition (Apel and Habermas) aim to establish a universal morality, guiding us on what is good and how we should behave.