What is Kant's Categorical Imperative?

Categorical imperative is Kant’s proposed way of evaluating our motivations for why we act. He talks about two kinds of imperatives (things that must be done:
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• Hypothetical imperatives, that have a specific end in mind, such as: To stop being hungry, I must eat something.
• Categorical imperatives, where our actions are based on moral principals, and are an end in themselves because they come from our moral goodness. They are not to attain something but to emulate what you would want to consider as a universal law.

He says, “Act in such a way that you treat humanity, whether in your own person or in the person of any other, never merely as a means to an end, but always at the same time as an end.” The way he puts it is complicated, but it is really a secular way of dealing with moral duty.

The Church has created moral duty using the motivation that we don’t want be punished with eternal damnation as well as imprisonment in this life. Kant says that it’s not because of our fear of hell that the good person chooses his actions, it’s because he has reasoned it out that it is his duty to be good and do good things.
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Possessing good will is one thing, but the reason we actually perform a good action is the result of our obligation to do the right thing. In other words, we ought to.