In 1529, Pedro de Cazalla, a scion of a prominent family of Jewish converts to Christianity from Toledo, claimed that no more than “a thread” connected men with God and that any mediation by the Church was unnecessary. This book explores the manyfold ramifications of this idea. It stems from the conviction that during the early modern period, the Iberian world was at once exceptional and paradigmatic. It was a laboratory of religious, juridical, and intellectual experimentation where, beginning in 1391, waves of mass con-versions compelled not only intellectuals but also ordinary women and men to reflect on the mechanisms of inclusion in Christian society. Because of its long history of violence, conquest, and assimilation, which began with the forced baptisms of Jews in 1391 and continued throughout the fifteenth and sixteenth centuries, early modern Iberia had to confront both the possibilities and the limitations of welcoming newly baptized Christians in its fold more than any other European region. Incidentally, here I use the term “assimilation” purposefully, even if it is technically anachronistic because it normally refers to the aftermath of emancipation, that is, the granting of full civic and political rights to religious minorities in the modern nation-state. For reasons that will soon become clear, I treat baptism as a form of emancipation. In pre-modern Europe, when the rights and obligations of any subjects of a political entity varied depending on their religious affiliation, the conversion of non-Christian minorities – regardless of whether it was voluntary or forcibly imposed – granted those who accepted baptism formal legal equality and new possibil-ities of upper social mobility.