There is an inevitable limit to understanding the internal experience of patients with whom therapists work in psychotherapy. The farther their experience is from that of their therapist, the more challenging this endeavor can be. Accepting that therapists cannot exactly know a patient's internal experience invites them to explore novel ways of appreciating another person's way of perceiving relationships, deriving meaning from them, and using their experience to motivate behavior. The concept of umwelt can be used as a metaphor to help therapists imagine the internal world of their patients, as shaped by patients' developmental, interpersonal, and traumatic experiences. Umwelt refers to the unique worldview created by a species' idiosyncratic perceptual organs and survival strategies. This first Psychotherapy Musings describes the concept of umwelt, applies it to the case of a patient with difficult-to-treat mental health problems, and explicates the benefit of this novel perspective.