Moral circle expansion is the attempt to expand the perceived boundaries of the category of moral patients. It has been proposed as a priority cause area (Anthis & Paez 2021) and as a heuristic for discovering cause X (Vaughan 2016).
Aird, Michael (2020) Collection of sources relevant to moral circles, moral boundaries, or their expansion, Effective Altruism Forum, May 7.
Many additional resources on this topic or related topics.
Anthis, Jacy Reese (2018) Why I prioritize moral circle expansion over artificial intelligence alignment, Effective Altruism Forum, February 20....