Written by the Swiss theologian Ludwig Lavater (4 March 1527 – 5 July 1586 in Zurich) in 1569, ‘Of Ghostes and Spirites Walking by Nyght’ was an early work upon the existence of ghosts. Translated into English in 1572, the book became the most frequently printed demonological works of the period. In the work Lavater came to the conclusion that ghosts or apparitions were not the souls of the deceased, but "either good or evill angels”. As seen by the plays of William Shakespeare (26April 1564 (baptized) – 23 April 1616), especially in Hamlet written between 1599 and 1602; the existence of ghosts and their ability to visit and affect the fate of the living, was an exceptionally popular idea during the Elizabethan and Jacobean periods.