Ethics & Moral Theory

Kant's Deontological
Ethics

A clear, memorable guide to Kantianism — how duty, reason, and universal law shape moral decision-making.

🧠 Master mnemonic: D-U-G-C — Duty · Universalizability · Good Will · Categorical Imperative
Section 01
Who Was Kant?
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Born in Königsberg, Germany (1724–1804) — never travelled more than 10 miles from home his entire life. Yet his ideas changed the world.
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So punctual that neighbours set their clocks by his daily walk. This love of order extended to his philosophy — moral rules must be precise and universal.
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Considered the most influential philosopher of the past 300 years. His deontological ethics still drives modern law, human rights, and AI ethics.
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Memory Hook

Think of Kant as the "Clock Man of Morality" — just as he was always on time, morality must always follow the same rules, without exception, every time.

Section 02
The Core Framework

"What makes an action right or wrong is the principle inherent in the action — not its consequences."

— Immanuel Kant

Kantianism is called Deontology (from Greek deon = duty). Unlike Utilitarianism which focuses on outcomes, Kantianism focuses on the act itself and the rule behind it.

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Duty-Based
Morality comes from obligations humans have to each other — not from what produces the best outcome.
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Universal
Moral rules must apply to ALL people, in ALL situations, for ALL of history — no special exceptions.
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Equality
Treat everyone equally and respectfully. People in similar situations must be treated in similar ways.
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Logical
Moral rules are grounded in reason, not emotion. A Kantian can always explain WHY an action is right or wrong.
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Good Will

Kant argued that intelligence, wealth, and talent are NOT always good — they can be used for evil. The only thing that is unconditionally good is a Good Will — the motivation to do the right thing, simply because it is right.

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Memory Hook

CONSEQUENCES DON'T COUNT — Kant is the opposite of "the ends justify the means." A surgeon who accidentally kills a patient trying their best did nothing morally wrong. A thief who accidentally saves someone by stealing is still a thief.

Section 03
Universalizability

The key test in Kantian ethics: could this rule work if EVERYONE followed it? If the rule self-destructs when universalized, it's morally wrong.

1
Identify the rule behind your action e.g. "I will lie when it benefits me."
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Universalize it — imagine EVERYONE follows this rule e.g. "Everyone lies whenever it benefits them."
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Does it contradict itself or become pointless? e.g. If everyone lied, no one would believe anyone → lying becomes pointless → contradiction!
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Verdict If it self-destructs → morally WRONG. If it holds up → potentially right.
✓ Can be universalized
Telling the truth — if everyone told the truth, communication works perfectly.
✗ Cannot be universalized
Murder — if everyone murdered those they disliked, no people would remain!
Section 04
The Categorical Imperatives

A Categorical Imperative is an unconditional moral law — it applies regardless of your desires, circumstances, or goals. Kant gave us two key formulations.

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Mnemonic: "U-E" — Universal law, treat as End

1st = ask "could this be a UNIVERSAL law?"  |  2nd = treat people as an END, never merely as a means.

1
The Universalizability Formula
Act only according to rules you could will to become universal laws
"Act only on a maxim that you could will to become a universal law of nature."
Example — Breaking Promises:
Could "I may break promises when convenient" be a universal law? No — if everyone broke promises, promises would become meaningless, defeating their own purpose. ∴ Breaking promises is morally wrong.
2
The Humanity Formula
Always treat people as ends in themselves, never merely as means
"Act so that you treat both yourself and other people as ends and never only as means to an end."
Example — Using someone:
Hiring someone knowing the job will disappear without telling them treats them as a tool (means to your end). You are not respecting their rational autonomy. Kant says: disclose the truth.
Section 05
Perfect vs. Imperfect Duties
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Mnemonic: "P-NE, I-PF" — Perfect = No Exceptions. Imperfect = Personal Flexibility.

Perfect duties are rigid and negative (don't do X). Imperfect duties are flexible and positive (do Y, but decide how/when).

Perfect Duty

Absolute Obligations

Strict — no exceptions, ever
Negative — duties NOT to do something
Universalizable without contradiction
📌 Examples: Do not lie. Do not murder. Do not steal. These apply always, no exceptions — even to save a life.
Imperfect Duty

Flexible Obligations

Flexible — some discretion in fulfillment
Positive — duties TO do something
Context-dependent in how/when you act
📌 Examples: Help others. Develop your talents. You must help people, but YOU choose when, where, and how — not every single person every time.
When duties conflict: Perfect duty always beats imperfect duty. Two perfect duties in conflict → Kant has no solution (a known weakness of the theory).
Feature Perfect Duty Imperfect Duty
Rigidity Absolute, no exceptions Flexible, discretionary
Form Negative (do NOT) Positive (you SHOULD)
Application Universal, always Context-dependent
Example "Never lie" "Help others"
Priority Wins over imperfect duties Yields to perfect duties
Section 06
Real-World Scenarios

Kant's ethics applied to actual cases — walk through the reasoning step by step.

1st Formulation

📚 Carla's Plagiarism

Carla is a hardworking single mother who runs out of time and submits a purchased essay as her own work.

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Her rule: "I may claim credit for work done by someone else."
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Universalized: If everyone submitted others' work, grades become meaningless → professors stop giving credit → rule defeats itself.
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2nd Formulation: She deceived the professor — treating him as a mere instrument to get a grade. That disrespects his rationality.
✗ Verdict: Morally WRONG by both formulations
2nd Formulation

🏭 Semiconductor Plant Disclosure

A plant closing in one year needs to hire workers now. Applicants from other states won't move if they know the plant is closing.

1
If info is hidden: Applicants are being used as tools to fill the vacancy — their rational decision-making is bypassed.
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2nd Formulation: Denying them key information treats applicants as means to the company's ends, not as rational beings with their own life plans.
✓ Verdict: Company MUST disclose the plant closure
Perfect Duty Conflict

🔫 The Murderer at the Door

You are hiding an innocent person. A murderer knocks and asks where they are. Can you lie?

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"Do not lie" — perfect duty. No exceptions.
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"Protect innocent life" — also a duty.
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Kant's answer: You cannot lie — even here. This is one of the most criticized aspects of Kantian ethics.
⚠️ Two perfect duties conflict — Kant offers no resolution
Section 07
Strengths & Weaknesses
✓ Case For Kantianism
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Rational: Based on logic, not emotion or popularity. Provides clear reasoning for why actions are right/wrong.
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Equal treatment: Everyone in the same situation is treated the same way — no favoritism.
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Universal guidelines: Moral laws apply to all people, across all of history. Stable and consistent.
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Workable: Provides actionable rules you can actually follow in everyday life.
✗ Case Against Kantianism
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Multiple rules clash: Sometimes two rules apply to one action — e.g. "keep your promise" vs "help the injured." No priority system.
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No exceptions: Even in extreme cases (hiding someone from a murderer), you cannot lie. Feels inhumane.
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One action, many rules: Actions can be described multiple ways — Kantian framework may not know which rule to apply.
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Two perfect duties conflict: When perfect duties clash (lie vs. preserve life), Kant has no answer. A critical gap.
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Bottom Line

Despite its weaknesses, Kantianism is considered a workable ethical theory — rational, consistent, and respectful of human dignity. Its legacy lives on in modern human rights law and professional ethics.

Section 08
Flashcards — Click to Flip
Term
Deontology
Click to reveal definition
Definition
Ethical theory based on duty (Greek: deon). Morality is determined by the nature of the action and its adherence to rules — not outcomes.
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Section 09
Quick Quiz

Question 1 of 5

Basics