Abstract
A recent philanthropic movement with advocates among high-profile tech entrepreneurs and philosophers, effective altruism (EA) has been widely disparaged for its flawed moral philosophy and conservative political implications. As philanthropic practice, however, it has been seldom studied. In this paper, we argue that claims to technoscientific expertise are central to how EA actors understand, legitimize, and take part in the production of philanthropic value. We analyze their practices of categorization, ranking and measurement as well as underlying technoscientific imaginaries and moral views through comparing three areas of EA intervention: neglected tropical diseases, cultured meat, and AI safety. We show how EA involves various and contested ambitions to direct knowledge production and redraw the boundaries of expert communities, shedding light on the centrality of technoscience in philanthropists' worldmaking ambitions.