Since the Protestant Reformation of the 16th century, anti-Catholic conspiracy theories have taken many forms, including the 17th-century Popish Plot allegations, claims by persons such as William Blackstone that Catholics posed a secret threat to Britain, and numerous writings by authors such as Samuel Morse, Rebecca Reed, Avro Manhattan, Jack Chick and Alberto Rivera. Theorists often claim that the Pope is the Antichrist, accuse Catholics of suppressing evidence incompatible with Church teachings, and describe Catholics as being involved with secret evil rituals, crimes, and other plots.