The shepherds' calendar in the 15th century
The Gospel offered by monks who praised Luther’s writings appealed to a number of peasants ; but the latter were gullible and easy prey to peddlers of various horoscopes arousing “holy” fears, endorsed by the Roman Church, and incidentally by Catherine de Medici. The Shepherds’ Calendar, written in the late 15th century (recently published again, PUF and Bibliothèque Bodmer, 2008) was a textbook with a lot of practical advice and instructive texts on star locations, but also a bold mixture of learning, snippets of knowledge and superstition.
Calvin's Warning was similar to that of Saint Paul's to the Galatians
Galatians 1. 6-7 : I admire how fast you are turning away from he who called you through Christ’s grace to move to another Gospel. Not that there is another one ; there are only people who make trouble among you.
Warning p.109 : For a long time curiosity prevailed, using the stars to “reveal” all that was to happen to mankind, to research and seek advice from them as to what was to be done. We will soon show, God willing, that it is all devilish superstition. It was actually rejected by common consent as harmful to mankind. Today it has surfaced again, so that many people who consider themselves well-meaning, and are said to be so, are almost bewitched.
The tricks of judiciary astrology : a movement from knowledge to speculation
Calvin never stopped stressing the fact that what was considered knowledge was knowledge of the natural order and arrangement in which God placed the planets and stars, to assess their function, characteristics and quality, and simplify it all to purpose and use (p.110).
But it could easily become speculation : Even if stars are signs showing when to sow or plant, to bleed or give a medicine, to cut wood, it does not mean that they are signs telling us when to wear a new dress, to trade merchandise on Monday rather then Tuesday… (Warning P.123.)
Calvin's hesitancy over possible links between astrology and medicine...
Calvin was aware of the progress in Knowledge and he demanded very rigorous reasoning. But it did not exclude caution, especially as far as health was concerned, a subject always popular with the horoscope “makers” :
It is also from true astrological science that doctors get their judgement to order bleedings or beverages, pills and other things at the right time. So we must confess that there is some agreement between stars and planets and the state of human bodies.
So be it, natural astrology will show that earthly bodies are somewhat influenced by the moon, as oysters that get filled or emptied ; just as bones are more or less filled with marrow as the moon increases or decreases.
In fact, in the 16th century those expanding knowledge in astronomy and medical matters knew one another, worked together and probably suggested possible links. Ambroise Paré, François Rabelais, Michel Servet – who worked a lot on blood circulation- all practiced such an eclectic approach.
The refusal to use astrology in predeterminism
Calvin questioned the use of predeterminism based on the position of the stars at birth, similar to hororscopes : should people born on the same day lead identical lives ? Should twins have the same fate ?
He maliciously emphasised the idea that a horoscope at birth would be arbitrary and in fact should be done at conception, since the length of pregnancies varies.
He also questioned the predeterminist contents of horoscopes, even more so if they were presented as God’s judgement : should we then consider that the movement of planets determines historical events, the outcome of battles, the conditions and time of one’s death, with no human involvement ?
Such reasoning leads only to a chaotic picture :
History claims that in Spain up to three hundred thousand men died in about twenty battles. Without further consideration, it is not difficult to see those who died in each company were born at many different astrological times. So, in such a multitude, Capricorn and Aries and Taurus fight so hard with their horns that all is confusion ; Aquarius pours so much water that a deluge ensues, Virgo is deflowered, Scorpio goes backwards, Leo strikes unnoticed with his tail, the Gemini twins seem to be one, Sagittarius’ shots are treachery, Libra is a fake, Pisces hides underwater, so one can no longer see anything (p.116).
But this has nothing to do with the Apocalypse :
They also declare the support of our Lord Jesus when he said there would be signs in the sky to announce the last coming…Indeed they should be excused as the Holy Scriptures are not what they seek…Our Lord Jesus, however, does not talk about a special constellation appearing naturally, but rather about something extraordinary unlike anything we know (p.125-126).