Background: This paper proposes that the adequacy of service delivery and caregiving to people who are disabled should be assessed using two criteria. One is the objective circumstance of living, which should be at a standard acceptable to the community at large. The other is a level of subjective wellbeing (SWB) within the normal range. Method: This latter criterion is a novel conception based on an understanding that SWB is homeostatically managed to lie normally within a narrow range of values. Results: People who have a disability are more likely than usual to have a fragile homeostatic system because of the additional life challenges imposed by their disability. Conclusions: The role of a caregiver is to provide resources and protection against strong threats to homeostasis, thereby ensuring that the person in their care has a normal-range level of SWB.