The frontispiece of the 1603 edition of Daemonologie
James I of Great Britain's reign was torn by religious and political strife. As James VI of Scotland, he had already come to believe that his life was threatened by witchcraft. In 1590 he took direct personal involvement in the North Berwick witch trials in the belief that an attempt had been made on his life by a coven of witches who had summoned a storm to threaten his fleet on a voyage from Norway.
In 1597, he set the tenor for the witch mania that swept across the country in the ensuing century and a half by publishing his Daemonologie - a philosophical treatise in which he set out the religious, philosophical and scientific basis for the existence of witches, and the moral case for pursuing them to justice. You can download the entire book in pdf format here.
His central thesis that witches were the devil's agents on Earth. As such, they were to be subject to divine justice and retribution for fomenting evil in Godly kingdoms. Daemonologie was no idle speculative book, but effectively a manual for the witch trials that he would unleash during his reign - and provided men such as Matthew Hopkins with a legal basis on which to instigate their own reigns of terror.
The book also hugely informed the culture of the time. Shakespeare's plays abound with ghosts and witches, for example, and the King's belief permeated throughout society. Suspicions abounded not just about witches as a result, but outsiders such as the recusants and Catholics were drawn into the maelstrom of belief in devilry and conspiracy. The Gunpowder Treason of 1605 merely served to confirm that the King was right: agents of the devil were afoot in the country and attempting to upset the natural order with acts of evil.
Such was James' influence that it seems only fitting that in the tale of Sawney Bean, it was he who is said to have personally led the hunt to pursue the legendary cannibal clan. In many ways, James I was England's paranormal king - and his influence on British culture is still felt in a myriad of ways even today.