Investigating physical experiences in order to understand the psyche is a cornerstone of early psychoanalysis. In describing the infant’s first year, Klein emphasized the emotional aspects of both mother and infant but neglected the physical aspects of the act of nursing. My re-reading of Klein’s concept of the splitting of the “good breast” and the “bad breast” is based on my survey of breastfeeding mothers’ descriptions, as well as information provided in breastfeeding guidebooks. Both claim that infants prefer one (good) breast while rejecting the other (bad) breast. Presenting the actual experiences of breastfeeding mothers, I argue for an interpersonalization of Klein’s theory, and claim that states of consciousness identified with the paranoid-schizoid position operate during breastfeeding in both mother and infant. Implications for psychotherapeutic treatment are discussed by linking the good/bad metaphor to actual nursing experiences.