This study, which is founded on an assumption of the unity of aesthetics and ethics, illustrates the reformative power of the moral imagination and sympathetic engagement in Mary Wollstonecraft’s first novella, Mary, A Fiction. Sympathy—wakened by the literary imagination and invoking the reader’s moral potentiality—is what links the literary and the ethical; the emotional exchange, the sympathetic fusion, that occurs between reader and text may extend beyond the pages of the novella into the real world. The affective experience of reading literature, which allows for imaginative perspective-taking, moves us to act in ways that make us more social, more resistant to injustice, and better equipped to enact necessary change. This study delineates the three-fold operation of imagination, sympathy, and affect in Wollstonecraft’s Mary, which extols a heroine who exemplifies the radicalizing power of affect and which itself has the power to effect a revolution in its readers.