Galileo, Order, and the Persistence of Reasoning through Aesthetics
Sunflowers follow the sun across the sky, and the moon controls the tides. Move a magnet over iron filings and the iron responds. You’ve already accepted action at a distance and celestial influence. Why dismiss planetary influence on human disposition outright?
In 1610 Galileo published Sidereus Nuncius, announcing discovery of four moons of Jupiter, which he called the Medicean Stars to flatter his patron. Scholars were divided. A contemporary astronomer, Francesco Sizzi, authored a small treatise in response, Dianoia Astronomica.
No summary of Sizzi’s reasoning does it justice. You need it in his words.
Just as in the microcosm there are seven ‘windows’ in the head (two nostrils, two eyes, two ears, and a mouth), so in the macrocosm God has placed two beneficent stars, two maleficent stars, two luminaries (sun and moon), and one indifferent. The seven days of the week follow from these. Finally, since ancient times the alchemists had made each of the seven metals correspond to one of the planets; gold to the sun, silver to the moon, copper to Venus, quicksilver to Mercury, iron to Mars, tin to Jupiter, lead to Saturn.
From these and many other similar phenomena of nature such as the seven metals, we gather that the number of planets is necessarily seven… Besides, the Jews and other ancient nations as well as modern Europeans, have adopted the division of the week into seven days, and have named them from the seven planets; now if we increase the number of planets, this whole system falls to the ground… Moreover, the satellites [of Jupiter] are invisible to the naked eye and therefore can have no influence on the earth, and therefore would be useless, and therefore do not exist.
There’s reasoning for you. Seven planets. Seven holes in the head. Case closed.
Today we know how the sunflower works. We know about phototropism, auxins, differential growth rates. We understand the mechanism. Francesco Sizzi didn’t.
His world system was built on regularities, from which he inferred relationships. He saw a universe whose underlying order could be read from recurring patterns.
For Sizzi, the universe was built upon sevens: seven planets, seven metals, seven days of the week, seven openings in the head. The cosmic order was complete. Galileo’s discovery was disruptive.
For a 16th century investigator of natural phenomena, the burden of proof was on the skeptic of long-held astrological knowledge. One reason astrology hung on so long was that no one came up with a satisfactory account of causation itself. In the 18th century, philosopher David Hume demolished the notion that we directly perceive causal necessity. We still debate what causation ultimately is. Like Sizzi, we observe regularities. We infer causes.
Sizzi was not defending ignorance. He was defending a conception of reality – and giving a nod to Pragmatism, a philosophy that wouldn’t emerge for another 300 years. The cosmos, as he understood it, was a web of correspondences. Harmony was the evidence. Symmetry meant something. The recurrence of patterns across different domains was evidence of a cosmic order. Rejecting those patterns in favor of four pinpoints of light visible only through a novel instrument did not seem rational.
We hold up Galileo as an example of speaking evidence to power. But most of us don’t reason as Galileo did.
We, like Sizzi, are drawn to elegant theories. Modern folk admire symmetry. We take pleasure in explanations that unify diverse phenomena. We find beauty persuasive. Often we discover reasons for believing something only after we have fallen in love with the shape of the idea.
We can’t blame Sizzi for seeking order. But he trusted the order he had already found more than the anomaly staring back at him from the telescope. The uncomfortable possibility is that we are usually closer to Sizzi than to Galileo.
We inherit the results of the scientific revolution, but not always its habits. Given a choice between a beautiful system and an inconvenient observation, the temptation remains as it was in 1610. The telescope has merely changed shape.
The Multidisciplinarian 