The problem of
moral responsibility is intimately connected with the
problem of free will, especially by modern "new compatibilists" who argue that free will may not exist but moral responsibility still does. Their arguments generally depend on obvious moral human behavior.
The first to use moral behavior to defend a compatibilist view of freedom was probably
David Hume. His "naturalism" was an empirical study of human nature.
Hume identified "moral sentiments" like praise and blame which arise from our
sympathy with others.
Hume's close friend Adam Smith wrote a fine essay on human sympathy called
The Theory of Moral Sentiments.
The most important recent thinker to employ this defense of moral responsibility was
Peter Strawson, who pointed to what he called our "reactive attitudes."
Whether or not determinism is true, Strawson claimed, we would still feel guilt and pride in our own actions, and see praise and blame appropriate for others who were deserving of being thought responsible for their actions.
We would have no such feelings for persons obviously incapable of being responsible. So the existence of "moral sentiments" and "reactive attitudes" is a sort of existence proof for moral responsibility.
However, we regard the use of moral behavior as a proof of human freedom as an
ethical fallacy.
Chapter 1.4 - Philosophy 
