Many speakers and writers use the terms 'exorcism' and 'deliverance' interchangeably, while others use the terms to distinguish 'formal' from 'informal' prayers. Still others place the need for Exorcism at the extreme edge of demonic interference (possession), with the need for deliverance only in cases of moderate harassment (obsession) by evil spirits. Some consider exorcism to be a command addressed to the demons, while deliverance is a prayer addressed to God. In this book, these terms have not been used as a vocabulary for making such distinctions.