As part of the “Solar Geoengineering: Ethics, Governance, and International Politics” roundtable, this essay examines dilemmas arising in exploring nonideal scenarios of solar geoengineering deployment. Model-based knowledge about solar geoengineering tells us little about possible climatic responses to malicious, self-interested, or competing deployments, and even less about political or cultural responses outside of the climate system. The essay argues that policy for governing solar geoengineering in a world of multiple states and uneven power relations requires a broader base for solar geoengineering knowledge, beyond that offered by modeling, and a better understanding of nonideal scenarios, especially those motivated by logics beyond reducing climate impacts. It highlights the interests of military and security actors in such knowledge, and the potential for it to facilitate securitization and further reduce the prospect of multilateral collaborative governance of geoengineering in the public interest. The essay concludes that further research can be ethically justified but must be comprehensively governed.