This chapter presents a brief assessment of evolutionary senses of "function" which reveal that a mixed evolutionary-based propensity interpretation is the most plausible. It provides the evolutionary-based propensity theory and the dual-homeostasis account to offer an evolutionary-homeostasis concept of health. Christopher Boorse's concept of health includes a contextualist concept of function. The implication of the evolutionary-homeostatic concept of health is that health is a state that admits of degree. Larry Wright and Boorse are both determined to satisfy the adequacy condition of offering a concept of function that ranges over artifacts and organisms. The evolutionary concept of health is able to make sense of both the genetic and phenotypic aspects of Down's syndrome and can likely make sense of other inherited disorders. Within the context of the concept of health, William Bechtel endorses the analysis offered by John Bigelow and Robert Pargetter.