The Doctrine of the blessed Trinity, briefly explained in a letter to a friend This book, "The Doctrine of the blessed Trinity, briefly explained in a letter to a friend", by John Wallis, is a replication of a book originally published before 1690. It has been restored by human beings, page by page, so that you may enjoy it in a form as close to the original as possible. This book was created using print-on-demand technology. Thank you for supporting classic literature.