Focusing on the various rounds of debates between the 1620s and 1640s on whether or how to seek peace or truce in the war with the Dutch Republic, this explores how agents and counsellors from different parts of the Spanish monarchy navigated the conflict between ideology and necessity-driven pragmatism in contexts of concrete decision-making. Directed at preserving and re-establishing dominion over the various realms of the monarchy, reason of state was at the heart of this weighing of principle and pragmatism. Agents were at the centre of a constant cycle of collecting and assessing information, projecting likely future courses and searching for the utmost expedience within the boundaries of royal conscience and obligations. What solutions were conceivable when attempts to preserve dominion over the Low Countries ran contrary to the demands of the Catholic faith and the preservation of the rest of the monarchy? Could special circumstances allow for special measures or concessions that might deviate from the princely obligations towards justice and the Faith? The chapter shows that as each decade of the war added to its own history, pragmatic arguments and solutions were often inspired by experience, together with a notion of extenuating necessity.