Kant’s Deontology

For Kant’s theory, all rational beings are always and necessarily  duty bound by the moral law: that is, the moral law is universal and necessary.   From this, Kant infers that:

NOTE: for Kant, these consideration suffice to rule out any from of utilitarianism as inadequate.

1) A good will is one that acts in accordance with the principles of morality and out of duty towards them.  It is the only thing good without qualification independently of its success. While other capacities, e.g., intelligence, gifts of fortune, talent, can  operate against morality (think of a clever thief), a good will always acts morally.
 NOTE:

2) The moral worth of a decision lies in the maxim according to which it has been  made, that is, the maxim on the basis of which the will (practical reason) has  operated.
A maxim is a principle of action, i.e., a general rule or policy one follows when  acting, e.g., “Give to charity,” “Tell the truth,” “Act in your own self-interest  only,” “Lie whenever it's advantageous.”
NOTE: 3) A maxim satisfying the Categorical Imperative is an objective maxim (a maxim  which any fully rational agent would follow), and an action stemming from that  maxim is moral.
Kant gives different formulations of the Categorical Imperative which he claims are  equivalent (whether they are is a matter of debate).   Two are especially important:
  1.  “Act only on the maxim through which you can at the same time will that it be a   universal law” (Universal law formula)
  2.  “Treat humanity 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.” (End in itself formula)

  3.  NOTE: Although strictly speaking there is only one Categorical Imperative, one can   call any maxim which satisfies (1) and/or (2), e.g., “Don’t lie,” a categorical   imperative.
4)  A categorical imperative must be distinguished from a hypothetical imperative, namely one whose justification depends on the perceived good of something  extrinsic to it.  For example, “If you want good business don't cheat your  customers” is a hypothetical imperative because in this case the justification for  the command “don't cheat your customers” depends on the desirability of having  good business.  By contrast, the justification for “Don't cheat” depends on the fact  that it satisfies both the universal and the end in itself formulas.
NOTE: .
5)  The universal law version of CI says “Act only on the maxim through which you can  at the same time  will that it be a universal law.”

6) The "end in itself" formulation of CI says:  “Treat humanity 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.”
 Rationale:
Since humans act morally and have a rational will, they have intrinsic objective  value and hence they are ends in themselves.  They are, one might say, the only  intrinsic moral values.  Since the value  of everything else is parasitic on that of persons and a means is less valuable than  its end, treating persons as means amounts to denying that they are ends in  themselves, that is, persons.
The meaning of the maxim is made clearer by the following:

 
A rational will (that which makes one a person) manifests itself in the link between one's values and one's actions. Treating people as means belittles the link; treating them as ends recognizes it as valuable.
 

7) The main problem for Kant's theory is its rigorism in that Kant’s ethics seems case-insensitive.  For example, he claims that one should never lie. But what should one do when someone's life is at stake? Should the Danish fisherman smuggling Jews to Sweden tell the truth to the Nazi officer on the patrol boat? Most of us would say “no”, but Kant says “yes”. (Notice that being silent won't do here).