Deontology

Introduction
Kant starts with a statement: the good will is the source of all moral worth.

He thinks that moral values are objective and universal, therefore any course of action (maxim) should be universalisable. That means that you should be able to logically want the entire world to follow your maxim.

The Categorical Imperative
You should only follow a maxim if you can logically will everyone to follow the maxim.

There are two ways a maxim can fail the Categorical Imperative:
 * 1) Contradiction in conception. It's impossible to actually imagine the entire world following your maxim. For example, the maxim "I will break promises to make money" would not be universalisable, because if everyone broke all promises, their would be no idea of promises so you can't possibly imagine a world where everyone follows the maxim. If a maxim commits contradiction in conception, you have a perfect duty to not follow it - it is never morally right to do it.
 * 2) Contradiction in will. It's possible to imagine the entire world following your maxim BUT it is illogical to do so - it would contradict your original motive. For example, the maxim "I won't help other people so that I am better off" commits contradiction in will because you would not be better off if no-one helped each other - we all needed help from other people when we were babies or when we drank too much pink flamingo. If a maxim commits contradiction in will, you have an imperfect duty not to follow it - it is not necessarily morally wrong to follow it, but it's often quite a good thing to not follow it.

The Humanity Formulation
Woah what, there's a whole another way of writing the categorical imperative? That's right, dear reader, Kant came up with two different ways of wording what he claims is the same thing. What a waste of time. The Humanity Formulation goes like this: "Act in such a way that you treat humanity, whether in your own person or in the person of another, always at the same time as an end and never simply as a means."Kant argues that a rational being cannot rationally consent to being used merely as a means to an end, so they must always be treated as an end in themselves. For example, enslaving someone to do your bidding is treating them as a means to an end: they're getting nothing out of the arrangement, (other than degrading treatment and a limitless source of menial tasks), there's nothing in there for them. On the other hand, should you pay someone to do the same thing, they are an end in themselves; their end is to be paid, and it is fulfilled.

Objections
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