Meagan S. Allen’s book Roger Bacon and the Incorruptible Human, 1220-1292: Alchemy, Pharmacology and the Desire to Prolong Life shows how alchemy, astrology and medicine were interconnected in the medieval world. Roger Bacon was a 13th century philosopher and Franciscan friar, who, like many others of the time, was influenced by both the Bible and medical works, and believed that the extension of life was a valid pursuit. 
Allen explains Bacon’s ideas in a consistently clear and lucid style. And while she mentions astronomy much more than astrology, at that time they were a united subject. But given the context, it seems to me that the astrological meaning is generally intended.
Adam and Eve were given the potential to live forever, eating the fruit of the Tree of Life in Eden, which would sustain them forever. But eating from the Tree of Knowledge, they had to leave. And human bodies have lost their balance compared with the much longer life spans of the biblical patriarchs.
Our bodies will eventually be incorruptible through God after the resurrection, and a physical resurrection that included both body and soul was the accepted idea. There would then be no tension between them, as both would be completely subject to the soul’s will.
Bacon was familiar with astrological works by Arabic authors like Abu Ma’shar and al-Kindi, and Greek works such as Ptolemy’s Tetrabiblos. Many texts attributed to Galen had also been translated into Latin by that time.
Not unlike today, the medical establishment offered little help for the aging process, since their focus was on disease. People could support their health with an improved diet and natural remedies that might help extend life (prolongatio vitae). And Bacon felt there were risks to relying on medical advice. Prescriptions needed to suit one’s age, constitution and horoscope, but doctors often weren’t good astrologers, alchemists, diagnosticians or apothecaries. Without these skills, treatment was left to guesswork and luck.
Lunar aspects should be considered when taking medicines, and herbs needed to be collected at the proper times. Helpful astrological patterns could pass celestial virtues onto alchemical medicines. Alchemical techniques (which might be termed astrological magic today) could also enhance food and stones to bring one back to health and prolong life.
The ideal was a corpus equale – a body with the elements in equal proportions, which was so balanced that it would be incapable of decay (as gold and the immortal resurrection body). Like everything else in the universe, stars and planets were made up of four essential elements and simple humors: sanguine blood (air), phlegm (water), choler (fire) and melancholy (earth). Our natal horoscopes give each of us differing elemental balances. The challenge, then, or the “secret of secrets” (secretum secretorum) lies in balancing out the qualities of the humors in the body.
A thousand years earlier, Galen and Hippocrates’ medicine also based human health on the balance of the four humors. As medical astrology still does today, alchemy was built on this foundation.
Bacon felt that the theory of the transmutation and purification of metals could be applied to human medicine, and that alchemical medicines could theoretically help us approach immortality. A universal health elixir would be perfectly balanced and therefore incorruptible, able to restore bodies to health. Bacon claimed he had seen it work with skilled doctors and patients.
Meagan Allen even shares the recipe, which included a combination of honey, fruit, seeds, spices and flowers, all fermented and boiled down with various powdered gem stones and gold, and placed “under the sky” for a week or so to take advantage of the “heavenly powers.” Other key ingredients could include the flesh and bones of the Ethiopian dragon (a large winged snake) and the Tyrian viper – which was good for old age and aided memory.
And best of all, no one need worry about a diagnosis, since the elixir had a universal nature that cured anything. A panacea, it did not require a diagnosis, and would balance humors, lessen pain, clear vision, calm disease and slow aging, support the brain, stimulate joy and prolong life.
Those interested in medical astrology, the medieval mind or alchemy’s connection with the cosmos should enjoy reading Roger Bacon and the Incorruptible Human, a well-researched and abundantly annotated work. Since Meagan S. Allen is a college professor, her book is another example of how ancient and medieval world views that support astrology continue to be legitimately explored today.
As an academic book, Roger Bacon and the Incorruptible Human is unfortunately rather expensive.
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