In 1437, and again in 1445, Pope Eugene IV issued bulls exhorting inquisitors to be more diligent in searching out and delivering over to punishment magicians and witches who produced bad weather, the result being that persecution received a fearful impulse.
But the worst came forty years later still, when, in 1484, there came the yet more terrible bull of Pope Innocent VIII, known as Summis Desiderantes, which let inquisitors loose upon Germany, with Sprenger at their head, armed with the Witch-Hammer, the fearful manual Malleus Maleficarum, to torture and destroy men and women by tens of thousands for sorcery and magic.

Similar bulls were issued in 1504 by Julius II, and in 1523 by Adrian VI.
The system of repression thus begun lasted for hundreds of years.

The Reformation did little to change it, and in Germany, where Catholics and Protestants vied with each other in proving their orthodoxy, it was at its worst.

On German soil more than one hundred thousand victims are believed to have been sacrificed to it between the middle of the fifteenth and the middle of the sixteenth centuries.
Thus it was that from St.Augustine to St.Thomas Aquinas, from Aquinas to Luther, and from Luther to Wesley, theologians of both branches of the Church, with hardly an exception, enforced the belief in magic and witchcraft, and, as far as they had power, carried out the injunction, "Thou shalt not suffer a witch to live." How this was ended by the progress of scientific modes of thought I shall endeavour to show elsewhere: here we are only concerned with the effect of this widespread terrorism on the germs and early growth of the physical sciences.
Of course, the atmosphere created by this persecution of magicians was deadly to any open beginnings of experimental science.

The conscience of the time, acting in obedience to the highest authorities of the Church, and, as was supposed, in defence of religion, now brought out a missile which it hurled against scientific investigators with deadly effect.