Illustration from mediaeval manuscript showing how to catch baby falcons by lowering a man over a cliff carrying a basket. Climbers will be interested in the rope technique. Frederick explained that if they were taken too young, they would be stunted and always scream when hungry.

Frederick's interest in science was famous. He was notorious as a sceptic, believing only evidence based on observation.

At his court, Frederick entertained astronomers, philosophers and mathematicians of note, including Leonardo Pisano (known as Leonardo Fibonaci, inventor of the eponymous series - 1, 2, 3, 5, 8, 13, 21 etc). It was via his court that mathematical innovations from the Arab world including the invention (discovery?) of zero were disseminated throughout Europe via the Italian merchants who used the new art of arithmetic to keep their accounts. Frederick also played host to specialists in anatomy, ethics, metaphysics, what passed then for chemistry and agriculture, as well as astrology (which didn't helped him achieve success, because it is, of course all rubbish, as Frederick may have come to realise). His frequent correspondence with Arab masters on scientific matters contributed much to the suspicion with which he was regarded by the Catholic establishment.

Frederick was a keen zoologist, writing prolifically on animal husbandry. His most famous text is "The Art of Hunting with Birds", which described the behavior and training of falcons. He enjoyed falconry, considering it a high and aristocratic art form. By far the most striking innovation in his work is the rejection of speculation in favour of observation: "Our intention is to set forth the things which are, as they are," he states, before launching into a number of corrections to Aristotle's writings on natural history: "in his work 'Liber Animalium'," Frederick wrote, "we find many quotations from other authors whose statements he did not verify and who, in their turn, were not speaking from experience. Entire conviction of the truth never follows mere hearsay."

Given the number of believers in creationism, homeopathy and all sorts of nonsensical hearsay that still roam the earth, the scientific revolution which Frederick started still has some way to go.

Frederick was also very interested in language, as could be expected of someone who spoke six languages fluently. He wanted to know whether at birth people were possessed of a "natural" language that was supressed when the learned their mother-tongues. Being of a scientific turn of mind, and being an absolute monarch, he decided to find out. He commanded that a number of children be cast into the wilderness, where they would grow up without human contact. The experiment ended in tragedy when they all died. OK, it's barbaric, but you have to admit, it is an intersting experiment. The world remains fascinated with the stories of Tarzan and of children raised by animals.

Some of Frederick's experiments were even more macabre, though always scientific. In one, he had convicts locked in an airtight room, waiting until they suffocated. He then watched carefully as the door was open, looking for evidence of their souls escaping. Again, it sounds, and is, barbaric, though not more so than burning someone or torturing them for heresy, as the Catholic Church was still doing centuries later. Frederick was trying to use observation to answer the most important questions of his day. He wasn't just making up completely implausable, unprovable theories, and then killing people who dared to disbelieve them, as were his opponents.

Despite his scientific leanings, Frederick was open-minded. In 1222, the leading religious ascetic St Francis came to visit Frederick at one of his palaces in Bari. Frederick laid on a sumptious dance by a notably beautiful courtesan. When St Francis proved resistant to her charms, Frederick noted that "his practice was even his precept," and spent many hours in discourse with the future saint.