“The Grand Duke has his own doctors, but thank you. How soon can he expect your horoscope?”

“Oh, let us say a week, or perhaps ten days—” As it was not the kind of thing that should be performed too quickly. “But in any case, as fast as I can.”

When Vinta was gone, without discussing remuneration at all, Galileo sat down heavily on a bench in his workshop.

It was a system that could be defended, if you granted its premises, which were probably true. Every event was the effect of some prior cause, everything moved in a woven tangle of cause and effect, which included of course the stars and planets. But unweaving the tangle was very difficult, and in that sense astrology was a doomed project, or at least quite radically premature, no matter its antiquity. But he could not say that to the Medici. And one could at least calculate the positions of the planets at the time of the subject’s birth. Do what everyone else did.

He groaned and called out for a new folio, quills, ink, a dusty old ephemerides. Vinta had left a big packet of papers containing the grand duke’s birth information.

For a long time he stared at all these things. He had paid sixty lire each for birth charts for the girls when they were born. He had only passed on one for Vincenzio because by then he could not afford it. He pulled the relevant tomes from the dusty top shelf on the back wall of the workshop. The basic text was Ptolemy himself: just as his Almagest covered all Greek astronomy, his Tetrabiblios described all their astrology. His description of celestial influences was derived from a mix of philosophers: Zeno, Pythagoras, Plato, Aristotle, Plotinus … Archimedes made no appearance. There was no way to apply to this problem the mechanics of Galileo’s hero.

In the more typical Greek way, Ptolemy and most of his sources saw the idios cosmos in the koinos kosmos, and vice versa; they spiritualized matter, materialized spirit. Fine; no doubt true. But the action at a distance! The unsupported assertions! Galileo cursed aloud as he read. The Tetrabiblios was simply an endless string of assertions. To use that as a basis for genethlialogy, the construction of individual horoscopes …

Well, Kepler had done it, and was still doing it. His Latin was so weird (if the problem did not reside in Kepler’s thinking itself), that Galileo was not sure what his books said; he had only paged around in them trying to find things he could understand. The astrological sections were worst of all in that regard. There Kepler was even more confusing than Ptolemy.

For one thing, Kepler called himself a Copernican, and Galileo tended to agree with him on that; but astrology was Ptolemaic. Perhaps Kepler’s incomprehensibility had to do with his attempt to make his astrology as Copernican as his astronomy, to save the appearances there as well as in the sky. St. Augustine had reconciled astrology with Christianity; perhaps Kepler felt he could reconcile it with Coperni-canism.

But there wasn’t the time to work through Kepler to find out. He had to set all the foundational issues aside and focus on Ferdinando. His chart marked the locations of all the planets at his birth moment, either square, oppositional, sextile, or in conjunction. Jupiter had been in the strong ascendant at his birth, Venus in conjunction. Consult the Tetrabiblios for the main significations for these luminaries. For Jupiter these were expansion, increase, honor, advancement, enjoyment of patronage, financial gain, joy, charitable instincts, travel, legal matters, religion, and philosophy. All these qualities suggested that Galileo himself must be a Jovian, but he knew already that Jupiter was not his Great Benefic, but rather Mercury. The slippery go-between; it didn’t seem right. Possibly he needed to make for himself a prosthaphaeresis, which was that correction necessary to find the “true” place of a planet, as opposed to its apparent or “mean” place.

But Ferdinando seemed to have been born under a good description. Good, good, and more good. Of course, almost everywhere in the sky was good. Clearly, no matter which benefic was in the ascendant, astrology focused on what good could be found in it. Ptolemy himself had noted this in the introduction to the Tetrabiblios—”one looks to the stars for the good that can be seen,” he had written—which was very convenient. Jupiter was definitely good. Enjoyment of patronage? Financial gain? Who wouldn’t want to be born under Jupiter!

He shrugged away his unruly thoughts and worked through the querents, the aspects and ceremonies, the conjunctions retrograde and indulgent, the oppositions and squares, houses and cusps, sextiles and tines. He applied the simpleton mathematics, so basic that he wondered if he could perhaps construct an astrological compass like his military one—or if perhaps his military compass already had the capacity to calculate horoscopes. He would have shared this joke with Marina had she been there. One more thing it could do.

It took two days to complete the work. Happily the horoscope genuinely predicted for Ferdinando long life and good health—both much in the ascendant, in fact, because of the current position of Jupiter in the zodiac. His death was most likely to fall twenty-two years in the future, at a square conjunction of quick Mercury and dour Saturn—not that ordinary horoscopes traditionally sought out such information, but Galileo had run the calculations through to their end, just out of curiosity. Astrology, he understood as he did this, was an articulated structure of hope. One never looked for ends of lives, even though the calculations could be made.

He wrote it all up, not including the end calculations of course, and had the finished drawings done by Arrigheti. He took the handsome foursquare charts and a fair copy of his calculations to the palace, and gave them in person to Vinta, who unceremoniously broke the seal on the leather case, which Mazzoleni had embossed with a gilt version of the Medici arms. Quickly he read the main page, nodding as he did so.

“Jove, Venus and the Sun, all in the ascendant. Good. His Highness and the grand duchess will be very pleased, I am sure.” A sudden piercing glance: “You’re sure about this?”

“The signs are very strong. His subjects can rejoice to know that their most benevolent grand duke is favored by Fortune and the stars.”

Vinta said, “God be thanked. For he complains of a gnawing inside him.”

Galileo nodded; he too was afflicted with such pains. He went home with the gift of a gold cup that could be sold for a decent sum to the goldsmiths.

Twenty-two days later, Ferdinando died.

When Galileo heard the news, his face burned. He cursed the servants scurrying away from his heavy hand. He stormed out of the house and wandered the streets of Padua, glumly imagining the next time he saw Vinta. For a moment he was even afraid; perhaps he would be blamed.

But given this world, in which all prediction eventually proved wrong, in which death touched down anytime, anywhere, such blame was unlikely. There was no reason to be more than embarrassed. He sent a long letter of condolences to the Grand Duchess Christina, and to Cosimo, with also a cover note of bafflement to Vinta—one which even delicately suggested the possibility of poison as an explanation for the discrepancy between Ferdinando’s stars and his actual fate. The celestial influence, he wrote, had somehow been overruled by a mundane cause.

And in the hubbub of the succession, no one actually seemed to remember Galileo’s most inaccurate horoscope. It was the kind of thing people forgot to remember. And it was also true that the new grand duke, Cosimo II, was an ex-student of his. The prospects for patronage were probably enhanced.

Still, the moment he had imagined finally came. Galileo visited the court in Florence to pay his respects, and was welcomed into the room by Vinta. Galileo entered already talking. “So sorry to hear of the grand duke’s unexpected and untimely death,” he began, but Vinta dismissed these sentiments with a flick of the hand—and with it a look of contempt, and even of a kind of unctuous complicity, as if Vinta was now in on a secret truth, which was that all Galileo’s mathematics were as fraudulent as astrology.