As alarm about climate change and calls for action intensify, solar geoengineering (SG) is seeing increased attention and controversy. Views on whether it should or will ever be used diverge, but the evidentiary basis for these views is thin. On such a high-stakes, knowledge-limited issue, one might expect strong support for research, but even research has met opposition. Opponents’ objections are grounded in valid concerns but impossible to fully address, as they are framed in ways that make rejecting research an axiom, not a conclusion based on evidence.