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Immanuel Kant was the greatest philosopher of the 17th and 18th centuries. His ideas are influential even today.

Kant looked at old philosophical problems in new ways. For example, we don't derive our notions of space and time from sense experience. Instead, we impose these structures on our sensations. The mind is active.

Ethics works the same way. Reason imposes its own abstract, formal laws on our actions. Morality ultimately rests, not on sense experience or feelings, but on reason.

These summaries and problems deal with Kant's Groundwork of the Metaphysic of Morals. These summaries and problems are copyrighted (c) 1998 by Harry J. Gensler but may be distributed freely.

The Groundwork

Kant's Groundwork defends morality against those who reduce it to self-interest, feelings, or empirical fact. Instead, the supreme moral principle is based on pure reason. Uncovering this principle is the goal of his book.

Basic ethical principles aren't "empirical" (from sense experience). Ethics gives necessary truths that hold for all rational beings. These can't be based on empirical facts about humans. Such truths, rather, are from pure reason; they are "a priori" (evident through thinking alone and not based on sense experience).

We need an a priori ethics because empirical motives (like self-interest) can lead us to violate our duty. Such motives lessen our moral worth; the highest motive is to do our duty, not from ulterior motives, but just because it's the right thing to do.

Good Will

Kant tries to uncover the principles behind common sense morality. He observes that only a good will is good without qualification (always good). A good will is good in itself, not just for what it produces. A will is good if it acts from duty (and other moral motives), and not just in conformity with duty. A grocer who gives correct change from a sense of fairness (and not from fear of getting caught) has a good will.

Reason's goal isn't to produce happiness (it's a poor means to this end), but to produce a will that's good in itself. Happiness, the satisfaction of all our desires, is too indeterminate to be a workable guide. Good will isn't the sole and complete good, but it's the highest good and the condition of the worthiness to be happy. The complete good is happiness combined with good will.

Hypothetical and Categorical Imperatives

Rationality has its own objective laws. Since we are only partly rational, we experience these laws as constrains -- as imperatives that we ought to follow. Such imperatives rest on grounds that are valid for every rational being as such.

Imperatives may be hypothetical ("If you want to fulfill end E, then you ought to do A") or categorical ("You ought to do A"). An ethics based on hypothetical imperatives is "heteronomous" -- since it involves "following the laws of another."

Categorical imperatives are difficult to understand but clear in their content. The basic categorical imperative is that we act on principle -- that we act on principles that we can will for everyone. An ethics based on categorical imperatives is autonomous -- since we "follow our own laws."

The Supreme Moral Principle

The supreme moral principle is the formula of universal law: "Act only on a maxim that you can will to be a universal law."

Kant applies his formula to two perfect (exceptionless) duties (not to commit suicide and not to make deceitful promises) and to two imperfect duties (to develop one's talents and to help those in need).

We can express the same idea more loosely in these ways: (1) "Act as if the maxim of your action would become a universal law of nature." (2) "Treat humanity, whether yourself or another, as an end in itself and not only as a means."

Morality and Freedom

Kant connects morality with freedom. To be free is to follow our own rational principles instead of just our desires -- to follow our own legislation -- to act on maxims that we will to be universal laws. Hence, to be free is to be moral. So freedom and morality are ultimately the same mystery.

We can't explain free will; we can only assume it and refute objections against it. We know that we're free by knowing that we have duties. We ought to have acted otherwise -- and so we could have acted otherwise -- and so we are free.

To see ourselves as free, we must see ourselves as part of two worlds: a sensible world and a higher intelligible world. Acting morally has supreme moral worth because through it we participate in a higher order of existence. This is the basis for the dignity of the human person as an end in itself.

Web resources

Click below to read the text of Kant's Groundwork:

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This set has 30 problems.