Why were masters of the occult respected but witches burnt?

It has long been acknowledged that alchemy, however bizarre its premises, is the fore-runner of modern chemistry, compelling a figure as rational as Sir Isaac Newton. Other aspects of Renaissance thought are harder to assimilate. In his study of five crucial figures of the 15th and 16th centuries, Anthony Grafton aims to demonstrate that astrology, angelology and conjuration were, if not central to the era’s world view, at least hard to extricate from its more respectable concerns.

His first subject, Faust, is little more than a sideshow, but significant in establishing the magus as a not entirely respectable figure, from which ignominy Grafton seeks to rescue him. The four who follow, Marsilio Ficino, Pico della Mirandola, Johannes Trithemius and Heinrich Cornelius Agrippa, each tussled with ancient learning, church teachings and the pressures and innovations of their modern world to build esoteric bodies of knowledge with the aim of the improvement of man.