Robert Calef wrote More Wonders of the Invisible World, a skeptical attack on Cotton Mather’s account of the Salem witch trials. Calef was a Boston cloth merchant, not a minister or court official, and his criticism made him one of the best-known contemporary opponents of the trials.
Calef assembled the work during the 1690s after corresponding with Mather and other ministers. It challenged the use of spectral evidence, questioned the proceedings against the accused, and reproduced material connected with the trials. The title deliberately echoed Mather’s 1693 book, The Wonders of the Invisible World.
Calef completed the manuscript in 1697, but it was printed in London in 1700 rather than Boston. Mather and his father responded in 1701 with Some Few Remarks upon a Scandalous Book. That response itself shows how seriously Calef’s critique had affected the Mathers’ reputation.
A common mix-up is confusing Calef with Thomas Brattle, another prominent critic who wrote an open letter against the proceedings. Calef’s distinctive contribution was a full published refutation centered on Mather’s claims.