This article examines the transition from a consent-based conception of politics to a ragion di Stato framework centred on the preservation of monarchical power in early modern Spanish economic thought. Focusing on the trajectory from Juan de Mariana to Martín González de Cellorigo and Sancho de Moncada, it argues that this shift entailed not merely a change in fiscal or economic doctrines, but a deeper trans-formation in the language and purpose of politics itself. While Mariana articulated a political order grounded in consent, property, and justice, later arbitrist writers in-creasingly subordinated these principles to the imperative of conserving and strengthening the monarchy. Drawing on the contrast between political reasoning oriented toward the common good and a governmental rationality concerned with stability, power, and survival, the article shows how economic arguments ‒ on tax-ation, money, and population ‒ were reconfigured as technical instruments of rule rather than objects of political deliberation. In doing so, it situates early seventeenth-century Spanish economic thought within a broader European shift from politics to government, highlighting the role of ragion di Stato in dissolving the boundaries between economic reasoning and the preservation of monarchical authority.