Book excerpt: It is important for Christians and Muslims to engage in respectful dialogue. However, it is not easy. The present book delves into the past for wisdom and guidance. Spanish theologian Martin Perez de Ayala (1504-66) wrote a catechism or Catecismo that was not published until more than three decades after he had passed away. Why was the Catecismo published posthumously? The search for answers to this question involved evaluating the Catecismo against thirteen other catechisms written in sixteenth-century Spain. This assessment generated timeless principles that can be used today by those who wish to have cordial conversations about Islam and biblical Christianity with their Muslim friends.