From In Character:
Compassion today is widely regarded as a good, and those who display it as good people. Indeed, many see compassion or some related virtue (e.g., empathy) as the core of goodness, as the virtue of virtues. It’s not only a private but also a public virtue, much cherished in our politicians. Even in international affairs, of all places, the apex of virtuous action is widely taken to be “humanitarian intervention” or the use of force to relieve suffering. Compassion has not always enjoyed so lofty and uncontroversial a status; will it someday once again relinquish it?
That compassion is natural to human beings there is no question. But does it pertain to our higher or to our lower natures? As even or precisely those who take compassion for a virtue acknowledge, it is an emotion. Can an emotion be a virtue? Yes, if the keynote of virtue is naturalness in the sense of spontaneity or authenticity. No, if what defines virtue is the perfection of our nature through the triumph of reason over passion. For this reason the long history of thought about compassion (stretching back at least 2,500 years now) has revolved around just this issue.
More here.