"sterile"

"Furthermore, Stephen Orgel and other New Historicists have pointed out the historical context of King James I's Daemonologie. In this framework, the "fourth witch" is a necessary narrative device; she represents the "domestic witch"—the hidden, intimate danger that exists within the household, as opposed to the wild, external threat of the heath."

"Gender and the Supernatural: Why does Shakespeare associate the subversion of the political order specifically with the subversion of female gender roles?"

"many critics argue that Lady Macbeth functions as a "fourth witch," bridging the gap between the supernatural prophecies and the physical world of political murder."