The big theological problem that Galileo's opponents had for Galileo wasn't the (not very convincing) biblical arguments that the sun moves and the earth stands still, but a theological objection to Galileo's inference from (a) the greater simplicity of the Copernican hypothesis over its competitors and (b) the fact that the hypothesis fits the data to (c) the truth of the Copernican hypothesis. The theological objection, as I understand it, was that Galileo was endangering the doctrine of divine omnipotence, since if there is an omnipotent God, he can just as easily have made true one of the less simple hypotheses that fit the data. (And, indeed, an earth-centered system can be made to fit the data just as well as a sun-centered one if one has enough epicycles.)
What Galileo should have said is that his argument does not, of course, establish the Copernican hypothesis with certainty, but only as highly probable, and that his argument had the form of the well-established theological argument ex convenientia, or from fittingness: "It was fitting for God to do it, God was able to do it, so (likely) God did it." Such arguments were widely given in the Middle Ages for theological views such as the immaculate conception of Mary. The application is that it is fitting for God to do things in the more elegant Copernican fashion, an omnipotent God was able to do things in such wise, and so (likely) God did it. Not only would the argument form have been one that Galileo's interlocutors would have been familiar with and friendly towards, but Galileo would have the dialectical advantage that he could not be reasonably said to be challenging divine omnipotence if his own argument depended on it. (Maybe Galileo did say something like this. I've seen the use of the argumentum ex convenientia in astronomy attributed to Kepler. Maybe Kepler got it from Galileo.)
And, to be honest, I think that all science is essentially founded on arguments ex convenientia. Which are good arguments.
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There is a problem with taking Heliocentrism as "the more simple" solution.
Epistemologically, it's the less simple one.
If I sit before a library and see a car move, I take it I am still, and the car is moving. This is taking the direct view of the observation of a moving car.
If I sit in a train and see a station move, I take it I am moving as observer (with the train) and the station is still. This is the parallactic view of the observation of a moving station.
Heliocentrism requires us to prefer the parallactic over the direct view. Geocentrism admits the direct over the parallactic view. So, Geocentrism is epistemologically simpler. And God ... potuit, decuit, fecit.
Your proposal mistakes both the nature of the quarrel and the grammar of Thomistic reasoning. The issue in seventeenth-century Rome was not a skirmish over God’s omnipotence, still less an allergy to simplicity, but the epistemic status of a bold physical claim. A Thomist does not deny that elegant theory is attractive; he denies that elegance, by itself, yields scientia. Aquinas distinguishes demonstration from fittingness the way a mason distinguishes a plumb line from ornament. Arguments ex convenientia are real, but they are never constitutive proofs. They belong chiefly to sacred doctrine, where revealed premises are given and the theologian may show the beauty, harmony, and propriety of what God has made known. They illuminate mysteries already received; they do not mint new contingent facts about the cosmos. To smuggle into natural philosophy the theological maxim potuit, decuit, ergo fecit is to change domains. In theology “fittingness” decorates faith’s certitudes; in physics it is at best an abductive hunch awaiting the hard bite of demonstration.
That is exactly why Bellarmine, speaking for a broad scholastic consensus, asked for one thing only: a true demonstration that the earth moves. Until then, treat heliocentrism as a powerful hypothesis. This is not timid piety; it is method. Thomism does not oppose inference to the best explanation, but it refuses to canonize it as knowledge while rival explanations secure the same phenomena. Galileo’s telescope shattered Ptolemy but not Tycho. The phases of Venus, the moons of Jupiter, the sunspots and mountains on the Moon—all of it devastated the old crystalline spheres, yet the geo-heliocentric Tychonic system still saved the appearances without moving the earth. Galileo’s sole “physical” proof, the tidal argument, was wrong. There was no measured stellar parallax, no Coriolis deflection, no Bradley aberration, no Foucault pendulum. In a Thomist’s vocabulary, the requisite propter-quid demonstration had not yet arrived. Until it did, a sober “as if” was rational; a triumphalist “thus it is” was premature.
Invoking divine omnipotence does not rescue the leap from probability to truth; it undercuts it. For in matters of contingent natural arrangement, God could have done otherwise, and the ratio convenientiae has no purchase on what He must do when we speak not of redemption but of orbits. The scholastic who says “do not bind Scripture to a cosmology until you have a proof” is not narrowing God’s freedom; he is refusing to enlist God’s taste as a premise in physics. Beauty and simplicity are real transcendental notes, and they often guide discovery, but they are not reliquaries of certainty. Ockham’s razor is a heuristic, not an article of faith. To argue that Copernicus is “fitting” is a theologoumenon at best; to argue that the earth moves requires empirical determinations whose absence no pious syllogism can supply.
Nor is it true that “all science is founded on ex convenientia.” Science certainly traffics in abduction, but abduction submits itself to crucifixion by experiment. The Thomist is not allergic to that traffic; he is its earliest defender. He insists on the climb from quia to propter quid, from effect to cause, from model to measurement. He gladly concedes Augustine’s rule: when a matter of fact is demonstrated, Scripture’s perennially true sense cannot be opposed to it; the literal must be read according to literary kind and authorial intention. But he equally insists on the other half of Augustine’s prudence: do not revise exegetical commonplaces on the strength of a theory that remains underdetermined by the data. That was Rome’s position. Far from being anti-science, it is exactly the discipline by which science matures.
Had Galileo said only that heliocentrism possesses superior explanatory power and simplicity and therefore merits provisional preference, he would have stood squarely within Thomistic method. Recasting his case as a theological ratio convenientiae, however, would not have strengthened it; it would have muddied categories. The Church did not need a pious varnish; she needed what the heliocentric cause would eventually receive: independent, convergent physical evidences. When those evidences arrived, the hypothesis ripened into truth, and the exegete did what Augustine had long counseled. In that sense, the scholastic caution Galileo chafed against was not a roadblock to science but the very guardrail that kept physics from confusing elegance with evidence and theology with astronomy.
What I meant by saying that all science is based on argumentum ex convenientia was something like this. We always have alternate theories that are more complex but that explain exactly the same phenomena just as well. Why do we think that God did things the simpler way? That he made gravity be Gmm'/r^2 instead of Gmm'/r^2.0000000000000000000000000001? He could have done it both ways, but the first one is more fitting.
And, amusingly, in the end both hypotheses about the solar system were equally mistaken: on General Relativity there is no fact of the matter whether the earth goes around the sun or the sun around the earth--it's just a choice of coordinates.
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