Deontology is the major alternative to utilitarianism in contemporary ethics. Whereas utilitarianism focuses on the consequences of actions for the purposes of moral evaluation, deontology focuses on the form of actions. Deontology concerns your moral duties or obligations.
There are two crucial things to keep in mind. The first is that for Kant, moral laws are subjective. That is to say the subject posits a moral law for itself.
But although moral laws are subjective, this does not mean that morality differs from person to person. The reason for this is that moral laws are produced by rational thought, and rationality, according to Kant, is the same in all human subjects. So if you are thinking rationally and I am thinking rationally, we will both posit the same moral laws.
Thus for Kant morality is both subjective and universal (to all rational agents).
Having said that, how do I know that my actions are moral? Kant proposed the categorical imperative as a way of evaluating the morality of our actions. Kant gives three formulations of the categorical imperative. You can think of these three formulations as three tests. If an action passes all tests, then you have a moral duty to perform that action. If it fails a test, then the action is immoral.
The first of the formulations requires that we act only according to maxims that could become universal without contradiction. For example, let's imagine that I want to steal a watch. If I steal the watch, then I am acting according to the maxim that theft is permissible. But can this maxim be universalized? No. If everyone were to act as if theft were permissible, then the notion of property would make no sense, and thus theft would become impossible. So the idea that theft is permissible is actually self-contradictory and thus not rational.
The second formulation asks us to act in such a way that we respect the humanity of others. If we act in a way that reduces people to means to an end, as tools that we use to accomplish our goals, then we act immorally. In its most extreme manifestations, the reduction of human beings to tools takes the form of slavery: human beings in a slave economy are just tools or machines used by their masters to accomplish the masters' goals. How do we avoid this? We should recognize in our dealings with other people that all people have their own ends and goals. For our actions to be moral we must respect the ends and goals of other people.
The final formulation recognizes the self-legislative nature of moral reasoning. The moral law comes from me, not from outside of me. The moral law is a product of my own reasoning. Thus the last formulation of the categorical imperative asks us to consider whether other rational beings would accept as rational the maxims that I posit. If other rational beings would not freely accept the rationality of the moral laws that I posit, then these laws are not universally binding and thus not moral.
If a moral law or maxim fails any of these tests, then it is not moral.
Having said all that, what are some possible criticisms of Kant's ethical system? How would Kant defend himself against these criticisms?
Take a possible course of action that one might take in business, derive the maxim upon which that course of action is based, and use the categorical imperative to test the maxim. Is the action moral or not?