Conversion has been an important issue for most of the universal religions - those usually associated with a founder, such as Christianity, Buddhism, Islam and Judaism - which have a mission to spread their message. Other religions have been less concerned with conversion except in so far as it has been a negative force for them to confront. This study explores how conversion has been understood by different religions during different eras, and includes a survey of the textual, legal, ritual, historic and experiential dimensions of the phenomenon of conversion.