Thomas Ady was an author and exposer of magic methods in 1600's England. After Reginald Scot published the famous Discoverie of Witchcraft in 1584 (revealing the secrets behind many magician's tricks in an effort to prove that they were entertainment rather than supernatural), King James published Demonologie in 1603, which in turn claimed that magicians did have supernatural powers.
Ady's book, A Candle in the Dark, published in 1655, took a very strong position that magic as an art form was not supernatural or demonic. His book was similar to Scot's earlier work, and even more clearly revealed the secrets behind a number of magical effects.
More importantly, Ady attacked the ideas and superstitions behind the belief in witchcraft using passages from the Bible itself. Combined with the explanation of exactly how certain magic tricks were accomplished, his book was a major factor in the public's reluctant realization that witchcraft was not real.
Ady's book was so influential and well-known that George Burroughs, a minister accused of sorcery (unnatural feats of strength) during the Salem Witch Trials, used the book as part of his defense. Unfortunately, his accuser had more political power than he did, and Burroughs was hanged.
A Candle in the Dark contains one of the first written references to the words "hocus pocus" as a magical phrase.
Credit: This biography originated on MagicTricks.com. Please credit this source if you use this information.