This paper introduces and defends the Blueprint View, a novel approach to understanding health and mental health in terms of abilities and design. It begins by addressing two key challenges for ability-based theories of health: the inclusion challenge (which abilities are relevant to health?) and the threshold challenge (to what extent do these abilities need to be present?). After rejecting influential existing approaches (Fulford 1989; Nordenfelt 2012), the paper develops its answer: the abilities relevant to health are those that the organism would have if all parts of the organism were fully functional. Inspired by Neander (1983), Wakefield (1992), and Griffiths and Matthewson (2018), selection processes determine full functionality.

In the second part, the paper extends this framework to mental health, addressing what distinguishes mental health from physical health. After critically reviewing alternative accounts (Wren-Lewis and Alexandrova 2021; Leder and Zawidzki 2023), it adopts the central tenet of Sanja Dembić's (2023) Rehability View, according to which mental health depends on the ability to respond to reasons.

This synthesis offers an account of mental health as a designed rational ability. It unifies physical and mental health under a single theoretical framework while distinguishing between them.