""A Letter Containing a Most Brief Discourse Apologetical"" is a book written by Dr. John Dee, a renowned mathematician, astronomer, and astrologer of the Elizabethan era. The book is a defense of Dee's controversial beliefs and practices, particularly his interest in the occult and his attempts to communicate with angels through the use of a crystal ball. In the letter, Dee addresses criticisms of his work and attempts to explain the rationale behind...