When the men involved in the government of the states of Renaissance Italy explained the basis of the principles by which they argued that political life and the conduct of affairs were, or should be, shaped, “reason” and “experience” were what they most frequently cited, sometimes separately, often together. Government records are the main sources for this study. Preambles to legislation, the records of council proceedings, and diplomatic reports and instructions have proved the most fruitful major classes of material; papers concerning or advocating reforms have a particular interest. One crucial consideration that has always to be borne in mind is the question of whose opinions are being voiced, particularly for documents written by chancellors or secretaries on behalf of a prince or a committee, although the book is not so much a study of the political principles of individuals as of the climate of opinion.