Kantian ethics are based on the theories of morality of Immanuel Kant, an 18th century philosopher. The system of ethics devised by Kant remains influential to this day, though it is far from universally accepted. Kantian ethics contain several main principles, though his work mostly boils down to the idea that certain principles are intrinsically moral, and that a moral person or society must observe these categorical imperatives in all situations. Critics tend to suggest that Kantian ethics oversimplify ethical decisions, and suggest that excluding all human emotion in favor of rational observance of certain principles is neither possible nor desirable.
One of the major cornerstones of Kantian ethics is the idea that it is the will of the person, not necessarily the consequences, that makes an action moral or not. If a person does something out of a sense of duty to moral law, then his actions have moral value. According to Kant, this means that if a person cares for his or her child out of the belief that caring for children is an important duty, he or she is acting ethically. If, however, a person cares for a child simply because he or she loves the child, this action is out of inclination rather than duty and not actually of moral value.
The way someone can know what moral law is, according to Kant, requires testing a principle against a system to see if it holds up. An example of a principle, known by Kant as a maxim, might be that if Joe is poor, Joe will rob someone else to get money. To test this maxim for morality, it must first be generalized, as in: any person who is poor should rob someone else to get money. Kantian ethics argues that this maxim falls apart at this point, for if everyone engaged in rampant robbery, the idea of personal property would dissolve, which in turn would meant that theft would be impossible as no one would really own anything. If a maxim fails the generalization test, then it can't be used as a categorical imperative or intrinsic moral law and shouldn't be used.
If a maxim stands up to the test of generalization, it may still fail the second test, which asks whether a person would want or will the generalization to be fact. The famous example used by Kant to explain this concept is called the bad Samaritan argument, which suggests that while a society would be possible where no one helped a neighbor in extreme distress, most people would not will that situation, for there would be no one to help them if they were in extreme distress. Maxims that a person would not will to be universal should not be acted on, according to Kantian ethics.
Criticism of Kant's principle of categorical imperatives usually comes against the idea that a moral law must be universal and allow no exceptions. For example, Kant claims that murder is universally wrong. Critics claim that this principle then suggests that a person should allow his wife to be beaten and raped rather than murdering her attacker. Kant's theory of imperatives, though quite rational, seems to be a utopian concept that cannot be fully realized in a complex society.
A second main principle to Kantian ethics suggest that people are intrinsically valuable and should not be used or treated as a means to an end. While this theory may seem blatantly obvious today, it certainly was not so in the 18th century. Kant stressed the rationality of other humans, which was a revolutionary concept in a world that engaged in slavery, repressed minorities, and guarded carefully against women's rights.