Esben, I would agree with Mill. That’s why I say that virtue, even for the Stoic, is instrumental to some higher good, such as harmonious and flourishing relationships with others, a just society, general welfare, etc.

To say that virtue is the chief good seems to me to be a sterile position akin to Kant’s when he said that the moral law ought to be upheld even at the cost of the destruction of the world. Well, if the world is destroyed, what good does the moral law do?