People ask me, “How long does it take you to write your books?” and I don’t know how to answer, because every book has been different for me. This book was the most difficult book for me to write and it took a long time to write, mostly because theological anthropology (the scholarly term for “the nature of the human person”) is a challenging subject. Thankfully, I had a lot of help along the way.

I would first like to thank Michael J. Cusick, who I mention in the book as my helpful counselor, therapist, and friend. Michael not only helped me get into the right place for me to write this, but also taught me key concepts and ideas that shaped this book in many ways.

Another person I would like to acknowledge is Fr. Adrian van Kaam. Though he passed over to glory many years ago, and though I never met him, his writings had a deep and profound influence on this book. I am grateful that he labored and studied and wrote so many wonderful volumes on the science of formation, and I hope that this book in some way leads people to his work. He is quoted in nearly every chapter, and I could have included many more of his brilliant insights. I am also grateful for Dr. Susan Muto, who worked for many years with Fr. Adrian and wrote many books with him. Thank you, Susan, for discussing Fr. Van Kaam’s work with me and helping me understand his great insights. One other person who helped me understand the writings of Adrian van Kaam is Dr. Rebecca Letterman. Thank you, Rebecca, for our conversations about his work. I recommend the book Susan and Rebecca wrote about the teachings of Fr. Adrian, called Understanding Our Story.

And as with most of my books, I am indebted to Dr. Dallas Willard. His theological anthropology, seen most clearly in his brilliant book Renovation of the Heart, has shaped my understanding, and thus this book, in too many ways to name.

Thanks to Joe Davis, who first gave me the idea that this book was needed.

And special thanks to Betsy McPeak, who was a graduate student of mine, and who served as a research assistant for me on this book. And more than that, she also collaborated with me on the soul-training exercises and the group discussion guide. Betsy, thank you for your wisdom and encouragement.

I would also like to acknowledge the great help that Chris Kettler, professor of theology and my longtime colleague at Friends University, provided for this book. Chris has read nearly all of my books and offered good theological and biblical feedback to help me avoid pitfalls, and to keep the ideas within the bounds of the great theologians who have gone before us, such as Thomas Torrance, Karl Barth, and Ray Anderson.

I would also like to thank Ben Davis for his careful reading of this book and the helpful feedback he gave me on many occasions.

My longtime friend Dr. Jeff Bjorck played a significant role in helping me navigate the challenging issues in psychology and theology that this book deals with. Jeff, thank you for taking so much time to read it carefully and thoughtfully, and for your excellent ideas and insights.

I would also like to thank Parker Morris, who read this book thoroughly and offered me great perspectives and ideas along the way.

My wife, Meghan, as always, is my supporter and champion, and without her support I could never finish something as daunting as writing a book, especially this one.

I also want to acknowledge my daughter Hope, for supporting me, encouraging me, cheering for me, and for having the courage to let me tell her story.

And I am grateful for my literary agent—but more importantly, “Writer Whisperer”—Kathryn Helmers, for standing with me from start to finish, and at crucial times helping me find my way when it was not clear.

I would also like to thank my editor, and friend, Cindy Bunch, at InterVarsity Press, who patiently walked through this book with me, and was the first person to read it in its entirety and offer great editorial suggestions.

I want to acknowledge the great help I was given by the two focus groups who read through the book, engaged in the soul-training exercises, and used the group guide in order to “field test” it. The first group, led by my sister and brother-in-law, Vicki and Scott Price, was their Apprentice Group in Salina, Kansas. Thank you Salinians!

And the second group of readers, at Chapel Hill UMC in Wichita, Kansas, are Heather and Mike Alumbaugh, Arlene Amis, Margaret Anderson, Dan and Jenny Bennett, Jayne Fry, George Houle, Jan Longhofer, David Nelson, Rene Patton, Andrew Peters, Lynne and Rus Pinkerton, Kelly Sooter, Diana and Jack Storm, Wes Darnell, Alaina Madden, and Deb Kivett. Your input and feedback was invaluable.

Finally, it may seem strange, but I would also like to acknowledge the Trinity—the Father, Son, and Holy Spirit—whose power and presence I felt while studying and writing and editing this book more than with any other book I have written.