Fundamental moral idea: Equality of all persons

Two ideas follow from this:

1. "One man ought never to be dealt with merely as a means subservient to the purpose of another." 
   
   [Clarification: this does NOT say that you can't ever be a means to the ends of another -- it says you can't "be dealt with" in that way, meaning that you cannot be treated as a mere means without your consent, as a means to your own ends. For example, someone else cannot make you their slave, but you can agree to work for them for wages.]
   
   
2. Justice requires equality (no one's ends count for more than anyone else's)

Two Consequences of these two assumptions:

1. Utilitarian plans of justice, such as punishing for "benefit of fellow citizens," is immoral, for it punishes someone as a means subservient to the purposes of others. 
   
   This point says that we cannot punish others simply because we would benefit from doing so. That would be wrong because it would allow us to punish innocent people, too, if it benefits us (our ends would count for more than yours).
   
   
2. The punished person must invite the punishment by wrongful behavior [punishment requires the CONSENT of the punished]: "undeserved evil which any one commits on another is to be regarded as perpetrated on himself."

The second consequence follows from Kant's basic moral rule, the categorical imperative (not mentioned directly in this reading): "Act only according to that maxim by which you can at the same time will that it would become a universal law." In other words, you can only give yourself permission to a behavior ("act according to that maxim") which you simultaneously give everyone else the same permission to do (you "will that it would become a universal law").

So if I steal from you, I give permission to everyone to steal from me.

Three consequences of the second consequence:

• ONLY the guilty may be punished. A system of punishment that does not protect the innocent is immoral.
• There must be a likeness or proportion of wrongful act and punishment.
• A substitute punishment (not the identical act) is often necessary, e.g., to address an abuse of power that occurs when a privileged aggressor (e.g., the wealthy and powerful) abuses their situation.

Under conditions of justice, the ONLY just purpose for punishment is "in order that everyone may realize the desert of his deeds."

This need for self-realization may require creative punishment. If someone powerful slanders someone who is not, a mere fine isn't sufficient as penalty (because they won't care about the cost of the fine). The powerful person must experience public humiliation in the presence of the person wronged.

In the case of murder, no substitute punishment can be sufficient to make the aggressor realize the significance of the wrong that has been done.

Conclusion: Capital Punishment is the just punishment for murder.