This is a work of moral psychology in the course of which is presented a theory on the nature of guilt. The point of departure is a psychological phenomenon that I call “scrupulousness.” Scrupulousness is present when someone is in doubt about the morality of a minor past action. He or she is obsessively driven to determine whether his act was right or wrong. The result for the individual is vexing preoccupation in a cycle of internal casuistry. I explain this unhappy phenomenon as the result of anxiety over guilt understood as moral staining. A moral stain is a persistent residue adhering to the self created by a past wrongful action. To better explain moral stains, I borrow Christine Korsgaard’s theory of personal identity as constituted by one’s choices. With the aid of Korsgaard’s theory, I then consider how a belief in guilt as moral staining accounts for the worry of the scrupulous person. The Postscript of the Report first considers whether scrupulousness is justified by the explanation I have furnished. I answer this question in the negative. I also consider how anticipation of scrupulous worry could drive a person away from morally ambiguous situations, sometimes preventing him from taking the correct course of action in a form of “moral cowardice.” The Postscript secondly explains the significance of investigating scrupulousness and moral staining for philosophers. I argue that moral staining captures important aspects of the phenomenology of guilt and that it correctly accounts for the reality of guilt as more than a mere psychological state or feeling. To exhibit these strengths of the moral staining view, I compare and criticize Herbert Morris’ prominent model of guilt as consisting in the severance of valued relationships. / text