ABSTRACTThis paper examines Thomas Aquinas’ and John Duns Scotus’ respective views on the action-passion identity thesis. This thesis, which goes back to Aristotle, states that when an agent causes a change in a patient, then the agent’s causing of the change is identical to the patient’s undergoing of said change. Action and passion are, on this view, one and the same change in the patient, albeit under two distinct descriptions. The first part of the paper considers Aquinas’ defence of this (...) thesis. The second part discusses Scotus’ attack on this thesis. As this paper shows, Scotus argues, against Aquinas and other scholastics, that action and passion are discrete entities inhering in two distinct bearers: action in the agent and passion in the patient. (shrink)