from The Internet Encyclopedia of Philosophy

Copyright 2001

18th century German philosopher Immanuel Kant (1724-1804) presents a
criterion of moral obligation, which he calls the categorical imperative.
Kant’s account of morality fits squarely into the deontological tradition
and is found in three principal books: The Foundations of the Metaphysics
of Morals (1785), The Critique of Practical Reason (1788), and The
Metaphysics of Morals (1798). Kant’s writings indicate that he was aware
of the moral traditions that went before him, such as virtue theory which
bases morality on good character traits, and consequentialist accounts
which base morality solely on the consequences of actions. In all of his
ethical writings, Kant rejects these traditional theories of morality and
argues instead that moral actions are based on a "supreme principle of
morality" which is objective, rational, and freely chosen: the categorical
imperative. Kant’s clearest account of the categorical imperative is in
the Foundations of the Metaphysics of Morals. 

In Section one of the Foundations, Kant argues against traditional
criteria of morality, and explains why the categorical imperative can be
the only possible standard of moral obligation. He begins with a general
account of willful decisions. The function of the human will is to select
one course of action from among several possible courses of action (for
example, my choice to watch television right now instead of going
jogging). Our specific willful decisions are influenced by several
factors, such as laziness, immediate emotional gratification, or what is
best in the long run. Kant argues that in moral matters the will is
ideally influenced only by rational considerations, and not by subjective
considerations such as one’s emotions. This is because morality involves
what is necessary for us to do (e.g., you must be benevolent), and only
rational considerations can produce necessity. The rational consideration
which influences the will must be a single principle of obligation, for
only principles can be purely rational considerations. Also, the principle
must be a command (or imperative) since morality involves a command for us
to perform a particular action. Finally, the principle cannot be one that
appeals to the consequences of an action, such as the joy I would receive
from watching television; for, appeals to consequences involve emotional
considerations. The only principle which fulfills these requirements is
the categorical imperative which dictates the universalizability of our
actions: "act only on that maxim by which you can at the same time will
that it should become a universal law." Morality, then, consists of
choosing only those actions that conform to the categorical imperative. 

In Section two, Kant explains key terms, presents different formulations
of the categorical imperative, and illustrates the categorical imperative
with examples of specific immoral acts. He begins by distinguishing
between types of imperatives. Imperatives in general are commands that
dictate a particular course of action, such as "you shall clean your
room." Hypothetical imperatives are commands that depend on my preference
for a particular end, and are stated in conditional form, such as, "If I
want to lose weight, then I should eat less." In this case, the command to
eat less hinges on my previous preference to lose weight. There are two
types of hypothetical imperatives. Problematic-hypothetical imperatives
involve rules of skill based on preferences that vary from person to
person (such as "If you want to be a doctor then you should go to medical
school"). Assertoric-hypothetical imperatives, by contrast, involve rules
of prudence based on the preference everyone has to be happy (such as, "If
you want to be happy, then you should go skydiving"). None of these
hypothetical imperatives, however, are moral imperatives, since the
command is based on subjective considerations that are not absolute. A
categorical imperative, by contrast, is an absolute command, such as "you
shall treat people with respect," which is not based on subjective
considerations. Thus, the supreme principle of morality is a categorical
imperative since it is not conditional upon one’s preferences. 

Kant continues by describing the sources of the above types of
imperatives. His discussion uses four technical terms: 

Analytic propositions: propositions that are true by definition, such as
"All wives are women." 
Synthetic propositions: propositions that are not true by definition, such
as "Jones is bald." 

A posteriori knowledge: knowledge attained through the five senses, such
as the fact that the door is brown. 

A priori knowledge: intuitive knowledge attained without use of the
senses, such as 2+2=4.

Kant argues that problematic-hypothetical imperatives are analytic or true
by definition, such as, "If you want to be a doctor, then you should go to
medical school." Assertoric-hypothetical imperatives are less clear since
the concept of happiness varies so greatly, as in the statement, "If you
want to be happy, then you should go skydiving." However, Kant believes
that even this statement is true by definition since if we fully
understand happiness, we will also know the means to happiness. Finally,
categorical imperatives are synthetic a priori, since the statement "you
shall treat people with respect," is not true by definition, and is not
known by means of the senses. Kant’s point is that the categorical
imperative involves a unique type of knowledge that is intuitive, yet
informative. 
In view of this background, Kant presents the single categorical
imperative of morality: act only on that maxim by which you can at the
same time will that it should become a universal law. Although there is
only one categorical imperative, Kant argues that there can be four
formulations of this principle: 

The Formula of the Law of Nature: "Act as if the maxim of your action were
to become through your will a universal law of nature." 
The Formula of the End Itself: "Act in such a way that you always treat
humanity, whether in your own person or in the person of any other, never
simply as a means, but always at the same time as an end." 

The Formula of Autonomy: "So act that your will can regard itself at the
same time as making universal law through its maxims." 

The Formula of the Kingdom of Ends: "So act as if you were through your
maxims a law-making member of a kingdom of ends."

According to Kant, each of these four formulations will produce the same
conclusion regarding the morality of any particular action. Thus, each of
these formulas offers a step by step procedure for determining the
morality of any particular action 
The formula of the law of nature tells us to take a particular action,
construe it as a general maxim, then see if it can be willed consistently
as a law of nature. If it can be willed consistently, then the action is
moral. If not, then it is immoral. To illustrate the categorical
imperative, Kant uses four examples that cover the range of morally
significant situations which arise. These examples include committing
suicide, making false promises, failing to develop one’s abilities, and
refusing to be charitable. In each case, the action is deemed immoral
since a contradiction arises when trying to will the maxim as a law of
nature. The formula of the end itself is more straight forward: a given
action is morally correct if when performing that action we do not use
people as a means to achieve some further benefit, but instead treat
people as something which is intrinsically valuable. Again, Kant
illustrates this principle with the above four examples, and in each case
performing the action would involve treating a person as a means, and not
an end.