Everyone knew the dangers of altering order. Yet being human and being informed by human intellect and curiosity - and not averse to the pleasures of power - wizards continued to tamper with the shape of things. They commanded the winds and waves, changed their own forms and those of natural objects, created illusions, summoned up the dead and looked into the future. All of them had some traffic with Satan or with his legions of demons: The Adversary was an ever-interested ally of anyone disposed to alter - and perhaps to damage - the structure of Creation. Some wizards, like the Franciscan friar Roger Bacon, or the Icelandic wizard Soemunder the Wise, or the Scotsman Michael Scot, trod their path warily and ended their lives more or less unscathed. Others, like Roger Bacon's sometime companion Friar Bungay or Wittenberg's vice-ridden John Faustus, paid for their power with blood.

Wizards of this era were scholars: Magic now was like a science, its poetry forgotten, and the powers of the wizards came in some part from years of diligent study. The price of living in a finely ordered world was the loss of the intuitive union with nature that the early wizards had possessed. If these later magicmakers were to master nature, they had first to comprehend its patterns and understand the network of correspondences and analogies that bound the universe into a single entity, a macrocosm of which man himself was the miniature reflection.

Central to their studies was the mastery of astrology; the examination of the paths that the planets took through the belt of constellations that girdled the earth. The figures of that great cosmic dance were everywhere mirrored in the world – even in the faces and bodies of humanity – and an understanding of the movements was a very powerful weapon indeed. The progressions of the planets were a map of the future.

The wizards studied terrestrial things, as well, and in particular the four elements – earth, air, fire and water – that they believed were present in varying proportions in all matter. This study found its most ambitious expression in alchemy, which, in its simplest terms, was an investigation of the proportions of the elements in metals, having as its aim the creation of gold. In gold, the king of metals, it was thought that the elements were perfectly balanced, as they were in any perfect earthly thing, including the healthy human body. The discovery of that balance would have given a scholar powers far beyond the creation of wealth, because it would mean that he would have the key to perfection.

The subject was so profound that it usually was investigated in secrecy, and the cryptic records that survive, replete with mystical symbols, are largely unreadable. The secrecy helped give rise to wonder-working rumors about all scholars – and not all scholars were wizards. The German sage and alchemist Albertus Magnus, for instance, was credited with the creation of a homunculus, a dwarfish servant with a human shape that walked, thought and obeyed. Unfortunately for itself and its creator, it talked too – or so the story goes. It prattled incessantly. Nothing could stop it, and the matter of its chatter was ineffably tedious. At last Albertus’ pupil Thomas Aquinas became so incensed with the creature that he smashed it into little pieces.

No tale could be more unlikely. Albertus and Thomas were men of towering intellect and irreproachable piety (both were eventually canonized), and neither man would have risked courting the creatures the wizards dealt with.