The Rule You Could Will
For Kant, an action is right only if the principle behind it — its maxim — could be willed as a universal law for everyone, and only if it treats each person as an end in themselves and never merely as a means. · 12 min
Consequentialism asked what your action would bring about. Kant asks a different question entirely: never mind the results — what is the principle you are acting on, and could you want everyone to act on it too? On his view an action is right or wrong because of the rule it follows, not because of how it turns out. A lie told for gain and a lie told from laziness share the feature that makes lying wrong: both treat the truth, and the person hearing it, as tools for your purpose. This folio lays out the two tests Kant thought could settle right and wrong without ever consulting the outcome.
Guess before you learn
You are short of money and consider asking a friend for a loan, promising to repay it while knowing full well you never will. Before acting, Kant says to ask yourself one question. Which one?
The first is the previous folio's question, and Kant rejects it: results are the wrong place to look. The third mistakes ethics for reputation. Kant's test is the second — universalizability. Imagine the principle behind your act made into a law that everyone follows. A world where everyone makes lying promises is a world where no one believes a promise, so promising itself collapses — and with it the very act you were trying to perform. The maxim destroys itself. That self-contradiction, not any bad outcome, is what marks it as forbidden.
9–12
3–5
Here is a test for whether something is fair. Before you do it, imagine everyone doing the same thing. If you break a promise whenever it helps you, imagine a world where everyone breaks promises whenever it helps them. In that world a promise would mean nothing — so your plan only works because most people are honest.
There is a second test too. Never use a person as if they were only a tool. You can ask a friend for help, but you must treat them as someone with their own choices, not as a machine for getting what you want.
6–8
Immanuel Kant called the supreme rule of morality the categorical imperative — a command that holds no matter what you happen to want. Its first form is a test of your maxim, the personal principle behind your act: act only on a maxim that you could at the same time will to become a universal law, followed by everyone.
Its second form looks at the people involved: treat humanity, whether in yourself or another, always as an end and never merely as a means. You may rely on people — you use the bus driver to get to school — but never merely as tools, bypassing the reason and consent that make them persons. An act that passes both tests is permitted; one that fails either is not.
9–12
Kant distinguishes two ways a universalized maxim can fail. A contradiction in conception arises when the maxim could not even exist as a universal law: universalize lying promises and promising self-destructs, so the maxim is incoherent, and the duty against it is perfect — binding without exception. A contradiction in the will is subtler: you could conceive the universalized maxim, but could not rationally will it — you cannot will a world where no one ever helps another, since you will sometimes need help yourself.
Perfect duties — do not make lying promises, do not coerce — hold always. Imperfect duties — help others, develop your talents — bind you to the end but leave room for judgment about when and how much. Ethics, for Kant, is not a hunt for good outcomes but the discipline of acting only on principles a rational agent could consistently give to all.
K–2
Before you cut in line, ask a question: what if everyone cut in line? Then there would be no line at all. If a rule only works when other people do not follow it, it is not fair.
And treat people as people. Your friend is not a tool for getting what you want. Ask if your choice is fair to them and treats them the way a person should be treated.
Undergrad
The theory's power is that it grounds rights and constraints that consequentialism strains to secure: because persons must never be treated merely as means, framing an innocent to placate a mob is forbidden outright, not merely outweighed. Kant located this dignity in autonomy — rational agents give the moral law to themselves — and pictured a kingdom of ends, a community in which each legislates rules all could accept.
The famous strain is Kant's own absolutism. Asked whether one may lie to a murderer at the door about where a friend is hiding, Kant said no — a perfect duty admits no exceptions. Benjamin Constant objected that this makes morality complicit in murder, and most Kantians since have sought a more careful maxim, or a hierarchy of duties, that keeps the theory's respect for persons without its rigid refusal to ever bend.
Postgrad
The universal-law formula invites a specification problem: how a maxim is described decides whether it universalizes. 'Break promises when convenient' fails; 'break promises to escape a lethal threat' may not — so the test seems to inherit its verdicts from a prior sense of which descriptions are morally apt. Interpreters answer differently: the logical reading (self-contradiction), the teleological reading, and Korsgaard's practical-contradiction reading, on which the universalized maxim undercuts the very purpose that motivates it.
Contemporary Kantian constructivism (Rawls, O'Neill, Korsgaard) reframes the imperative as the procedure by which rational agents construct binding principles, rather than as a set of intuited moral facts — offering an answer to where normativity comes from without appeal to consequences or divine command. The standing question is whether so formal a procedure can, alone, deliver a determinate morality, or whether it must draw its substance from the practical judgments it was meant to justify.
maxim
The personal principle behind an action: what you propose to do, in what circumstances, and to what end. Kant tests the maxim, not the act's results, by asking whether it could hold as a law for everyone.
The lying promise is Kant's own worked example, and running it slowly shows both tests at once. Start by putting your maxim into words — not a vague urge but a precise principle. Then universalize it and look for the contradiction. If the universal version cannot even hold together, you have a perfect duty and the act is forbidden. Finish with the second test, which usually agrees: ask whether the plan treats the other person as an end who could consent, or merely as a means to your purpose.
Run both tests on a lying promise — the steps fade as you master them
If everyone made promises they meant to break, no one would believe a promise — the practice collapses.
No — it needs promising to work while destroying it. That is a contradiction in conception.
Forbidden — a perfect duty not to make lying promises.
Yes — it uses them as a tool for money and bypasses the consent they would withhold if they knew the truth.
Yes — both forbid the act, for reasons that never mention the outcome.
Why is this true?
Why does the lying-promise maxim fail Kant's first test, when a single lying promise might well succeed?
Because the test asks about the maxim made universal, not about your one act. A single lie can trade on everyone else's honesty; but if everyone acted on the same maxim, no promise would be believed and there would be nothing left to exploit. The maxim works only as an exception to itself, which is exactly the contradiction Kant is pointing to.
Between them, the last two folios stake out the great divide in ethics: judge the act by its results, or judge it by its principle. Each catches something the other drops — consequences that plainly matter, and rights that plainly do too. A third tradition refuses the terms of the contest altogether. Instead of asking which act is right, it asks what kind of person you should become, and treats the good life, not the single decision, as the true subject of ethics. That is the next folio.
Practice — new ink and old, interleaved
1.Order into standard form: “Whales are mammals, and no fish is a mammal, so no whale is a fish.”
- Whales are mammals.
- No fish is a mammal.
- Therefore, no whale is a fish.
2.Four reasons are offered against a factory closing a polluting plant. Which one is the consequentialist reason?
3.“Every swan anyone has recorded has been observed carefully, and the last thousand were white, so the next swan will be white.” What kind of argument is this?
4.From folio 9: Kant held that 'ought implies can' — you are bound by a duty only if you are able to obey it. Which view of freedom does that fit best?
5.Rebuild Kant's universal-law test, in order.
- State the maxim behind your act.
- Imagine everyone acting on that same maxim.
- Check whether the universal version contradicts itself.
- If it does, the act is forbidden.
6.From folio 10: a consequentialist and a Kantian both oppose the lying promise, but for different reasons. Which is the consequentialist's?
7.In one sentence, explain what the word 'merely' adds to 'never treat a person as a means.'
8.From memory: what is the difference between a perfect and an imperfect duty for Kant?
A perfect duty binds always and without exception, and its violation is a contradiction in conception — for example, not making lying promises. An imperfect duty commits you to an end, such as helping others or developing your talents, but leaves latitude about when and how to act on it.
How close were you? Grade yourself honestly — it sets your review date.
9.Which reason for not cheating is a Kantian one?
10.Without looking: state the mind–body problem, and name the two great families of answer.
The mind–body problem asks how conscious experience relates to the physical brain; the two families of answer are dualism (mind is a distinct, non-physical thing) and physicalism (mind is the brain at work).
How close were you? Grade yourself honestly — it sets your review date.
11.From folio 3: Kant argues 'Only universalizable maxims are permissible; this maxim is not universalizable; so it is impermissible.' Is the form valid?
12.A friend says 'the mind is obviously just the brain — end of story.' What has the friend skipped over?