(You can find a more detailed summary of Kant’s ethics here.)

Kant’s most basic presupposition regarding ethics was his belief in human freedom. While the natural world operates according to laws of cause and effect, the moral world operates according to self-imposed “laws of freedom.” Here is his basic argument for freedom:

1. Without freedom, morality is not possible.

2. Morality exists, thus

3. Freedom exists.

The first premise is true because, according to Kant, determinism undermines morality. The second premise Kant took as self-evident, and the conclusion follows from the premises. Kant also believed that freedom came from rationality. Here is his argument:

1. Without reason, we would be slaves to our passions (lust, envy, avarice, etc.)

2. If we were slaves to our passions, we would not be free; thus

3. Without reason, we would not be free.

We now have the basis upon which to connect between reason and morality.

1. Without reason, there is no freedom

2. Without freedom, there is no morality, thus

3. Without reason, there is no morality.

Kant believed moral obligation derived from our free, rational nature. But how should we exercise our freedom? What should we choose to do?

Kant’s ethics is the study of our duty. Since we are free, rational beings we can choose between actions, unlike non-human animals who are guided by instinct. Moral actions are actions where reason leads rather than follows. Such actions must take into account other beings that act according to their own conception of the law. Put simply, to be moral we ought to conform our free will to the moral law; that is our duty.

Kant says the only thing that is completely good is a good will—the desire to conform itself to the moral law. But what is the moral law? Kant assumes that there is a moral law, and that there is some rational representation of the moral law that we can understand. And exemplars of laws are laws of nature which are characterized by their universality. So the moral law, he argued, must be characterized by universality too. Just as an equation of the form a(b+c) = ab + ac is universally applicable and needs only to be filled in by numbers, the moral law must have an abstract formulation by which to test actions.

Kant had seized upon the idea of universalization as the key to the moral law. To universalize a principle of our action we ask, “what if everybody did this?” According to Kant, we should act according to a principle which we can universalize with consistency or without inconsistency. This is what he calls the categorical imperative. By testing the principle of our actions in this way, we determine if they are moral. If we can universalize our actions without any inconsistency, then they are moral; if we cannot do so, they are immoral.

For example, there is no logical inconsistency in universalizing the maxim, whenever we need a car we will work hard to earn the money. However, there is something inconsistent about universalizing the maxim, whenever we need a car we will steal it. A world where everyone stole cars would be a world where there were cars to steal but no cars to steal—since they would all already be stolen! (This is the basic idea, this is actually quite complicated.)

Of course, we can act contrary to reason because we are free, just like we can say that 2 + 2 = 6 or we can say that there are round squares. But we violate reason when we say these things just as, for example, bank robbers violate reason when they rob banks. Why? A bank robber wills a world where:

banks exists as the necessary prerequisite of the bank robbery intended and banks don’t exist as the obvious consequence of bank robberies.

Kant’s basic idea is something like this. If I say you can taste my wine, I should be able to taste yours. Moral actions are rational, immoral actions are irrational.

In short, we act ethically if we freely conform our will to the moral law which it understands as the categorical imperative. The imperative prescribes action that are rationally consistent. If we act in this way, we may not be happy, but we will be moral. We will have done our duty.

(You can find a more detailed summary of Kant’s ethics here.)

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