On 12 June 1635, the count of Castrillo, a member of the council of Castile and nephew of the count-duke of Olivares, composed a hastily scribbled note to his confessor. In his note Castrillo had a number of pressing questions to ask. Can the king require his subjects to serve him personally in arms? What obligation do they have to serve him with their wealth, especially the members of the aristocracy and the bishops? What is the obligation of the Cortes to concede taxes? Does it matter whether the war which serves to justify the taxes is fought at home or abroad? On what grounds can a member of parliament, a proctor (procurador), vote for taxes in good conscience? What is the extent of the Cortes' obligation to approve new taxes when it is obvious to all that the kingdom is impoverished? In short, ‘how, given the widest latitude possible, might His Majesty best be served within the limits of conscience?’ These questions, along with the confessor's careful response, provide a unique and valuable insight into the political culture of Olivares' Castile – a culture in which theology and a preoccupation with informed conscience significantly shaped the context in which political decisions were made.

At the time Castrillo raised his questions, the atmosphere at the royal court in Madrid was tense. Spain had recently declared war on France and military preparations were in high gear. Castrillo's own preoccupations were financial.