Williams's name for the deep commitments that give a life its character — not preferences, but the projects without which the agent would not recognize her life as her own. The units of identity the AI transition is reorganizing faster than new ones can form.
Ground projects are the commitments constitutive of an agent's identity — the things without which her life would cease to be recognizably hers. Williams introduced the concept to distinguish them from ordinary preferences, which can be swapped without existential cost. The scientist whose life is organized around inquiry, the engineer whose identity is inseparable from building, the craftsman whose self is constituted by mastery — these are persons whose ground projects are not external to their identities but internal to them. Asking such a person to abandon her project is not asking her to change her preferences but asking her to become someone else. The AI transition threatens ground projects by transforming the practices around which they were formed, and threatens their replacement by denying the temporal space in which new ones could constitute themselves.