“Sympathy” was a key term in two of the liveliest discourses of the eighteenth century. On the one hand it provided the underlying foundation of influential moral philosophies from Rousseau to leading figures of the Scottish Enlightenment. On the other hand it was a principle term of contention in the battleground of theatrical practice and theory. While sympathy provided the first keystone of human epistemology for sentimentalist philosophy, it represented the final telos for sentimentalist theater. This essay analyzes the mechanics of sympathy in Adam Smith’s Theory of Moral Sentiments (1759) and Gotthold Ephraim Lessing's Miss Sara Sampson (1755). It claims that when one begins to look at the rhetoric of sympathy in the discourses of philosophy and theatre side by side, one notices that the philosophers constantly borrow the language and imagery of theatricality while the dramatists repeatedly make assumptions about ethical distinctions. The essay shows that despite this affinity, each of the two discourses seems to have precisely the other’s focus on compassion as its own blind spot.