“Affect,” writes Brian Massumi in The Politics of Affect, “is this passing of a threshold, seen from the point of view of the change in capacity.” Taking his cues from Spinoza and Deleuze, Massumi’s affect is the simultaneous capacity for affecting and being affected, a movement that bespeaks potentiality of corporeal and incorporeal movement. However exciting Massumi’s Deleuzean notion of “change in capacity” might be, the always-already nature of change within his model in some ways takes as a foregone conclusion one of the most important concerns of Enlightenment accounts of affect—the question of how affects change. A hydra-esque question, it entails queries as to how one emotion turns into another, how the trajectory of affect might change (from positive to negative, for instance), how the field of potentiality inherent in affect might shift, and how changing feelings might change people (including our ideas of the human) and vice versa. While Spinoza in the Ethics theorizes a monadic universe in constant motion, his more classically Enlightenment schematization of emotions such as hate and love often exist in dyadic pairs, in strength and weakness, and through association among objects and other emotions. How these emotions change from one to another often appears within a dualistic axis that Silvan Tompkins, in a different way, takes up in his paired schema of affects such as “interest/excitement,” “shame/humiliation,” or “contempt/disgust.” David Hume takes up the associative nature of affects in the second book of A Treatise on Human Nature and places great weight on the pull of pleasure and pain in creating opposite passions such as pride and humility, love and hatred. Yet, Hume does envision bodily change (via figures such as the Eolian Harp) with moments of change not defined by oppositional, individualistic, or binaristic logic. These figures gain fuller affective force in Percy Shelley’s Prometheus Unbound with the vibrational songs of the Oceanides that transform the negative affects of the Earth into a wider field of potentiality, or in Mary Prince’s History with its antiphonal and haptic repetition to transcend the binarism of sympathy’s like-me/not-like-me. Such shape-shiftings, which enlarge Monadism and Associationism with chemical ideas of affinity and hard labor’s familiaryt with reciprocal touch, offer a version of affect that posits change itself as ontological transformation.