Deeply rooted in theological, scientific, and legal considerations, Wier's thought transects that of his time: his poor old witches, elderly and infirm, continue to this day to evoke compassion rather than terror or distain. For around two centuries, European cultural debate celebrated Wier's legacy, and his defence of witches remained the test bed for all those who wished to try and tackle the question of witchcraft. Although unable to guide humanity out of the labyrinth of spells, Wier certainly showed the way and traced the path that was to direct later generations, laying claim to the right and duty of scholars to go against the flow, with strong ethical motivation, contrary to the spirit of the times. Later, in the nineteenth century, with the advent of social sciences and Positivism, Wier's work was read from an anachronistic and warped perspective: the point from which we took our inspiration.

Readings, studies, and practical medicine in particular placed Wier in direct contact with reality, allowing him to discover, behind nebulous accusations and dogged suspicions, deceit, superstition, and credulity. Concerning the question of whether witchcraft was reality or illusion, Wier did not hesitate in his response: it was an illusion. According to his judgement, demonic action very rarely intervened in reality. Furthermore, this intervention was in the body of the presumed witches, who convinced themselves of the impossible due to their melancholy; their ignorance did the rest. Wier did not know how to entirely break the chains of traditional knowledge (remaining faithful to Galenic theory) as some of his contemporaries did; he lacked the strength and intellectual audacity of others such as Reginald Scot, who denied demonic activity. However, from his essentially orthodox and conventional position, he nevertheless managed to raise an appeal. Wars and persecution condemned many to Satan, a dramatic consideration that contrasted with the evangelical message. Through his defence of witches, Wier reclaimed the meaning of charity and pity, thus seeking to halt the spilling of innocent blood. His mission was an attempt to save humanity from eternal perdition by offering everyone a chance of redemption.

Aware of the difficulty of his both task and the vehemence of his adversaries, Wier expounded his theory with a pars destruens and a pars construens.