CT 3.2, The Heavenly Bodies

Last updated on: December 23, 2014 at 5:49 pm by willduquette

CT 3.2, The Heavenly Bodies 2014-12-23T17:49:30-05:00 willduquette

LOGO Patheos Explore the world's faith through different perspectives on religion and spirituality! Patheos has the views of the prevalent religions and spiritualities of the world.

Continuing my look at Chapter 3 of the Compendium Theologiae. The complete series is here.

Thomas was talking about how one thing moves (i.e., causes change in) another thing, and referenced Medieval astronomy as an example. Because the motion of the heavenly bodies figured largely in Aristotle’s notions of the Unmoved Mover, we should spend a little time on it.

To Thomas, as to Aristotle—and, in fact, to everyone who lived before the invention of the telescope—the stars and planets seemed to be of an entirely different order of creation than the things of this earth. This is hard for us to understand: we are so used to thinking of outer space as so much vacuum, the stars as so much incandescent gas, the planets as moving according to the laws that govern the movement of the wind, or of avalanches, or of cars on the freeway. But until Galileo and his contemporaries used telescopes to look at the stars and planets and saw so much up there that was reminiscent of so much down here, the “superlunary” bodies were thought to be perfect, incorruptible spheres, of a higher nature than lowly terrestrial matter.

Astronomy, to the predecessors of the telescopic age, wasn’t regarded as a physical science at all, but as a branch of mathematics. It was more about being able to predict where the heavenly bodies would be seen at a particular time than it was about understanding the motion of brute matter. The goodness of a model of the heavens was judged based on its simplicity and the quality of its predictions, not on any modern notion of the laws of physics.

Aristotle went beyond this, to ask why it was that the heavenly bodies moved. They were not moved by the wind, as a leaf is blown in the autumn, or by the water, as a log in a river, or by the hand of man, as trees are fashioned into a house, and yet they moved. He reasoned that they must be moved by each other, not indeed as you or I move a chair from one place to another, but by what he called “final causality”. And he reasoned that those changes we see on earth that seem to have no obvious cause must be driven in a similar way.

He was wrong; but Aristotle was a skilled observer, and in many ways he was also right. He had no notion of gravity, that discovery of Isaac Newton, but we now know that the motion of the planets around the sun is determined by the relative masses of the sun and the planets. Together, the gravity of the sun and the moon drive the tides (a fact quite familiar to the ancients), and the earth’s motion relative to the sun drives the seasons.
In short, Aristotle’s notions are not entirely farfetched, even if he was limited by the nature of his instruments: his own two eyes. Newton famously said that he stood on the shoulders of giants, and Aristotle was one of them.

To Be Continued.

Believing Thomas

compendium theologiae

heavenly bodies

Thomas Aquinas

Previous Post

May 11, 2014

Lumen Fidei: Hearing His Voice, Seeing His Face

Next Post

May 13, 2014 Review: Something Other Than God, by Jennifer Fulwiler

Browse Our Archives

Select a Category Admin App o' the Morning Ask the Dogmat Believing Thomas Bits of Fiction Blasts from the Past Bootstrapping the Interior Life Catholic Mom Christian Living Deep Thoughts from the Doghouse Dominicana Evangelii Gaudium Interviews It Was A Dark and Stormy Night Links to This and That Lumen Fidei Meme Watch On Writing Operation Gratitude Pedant Errant Photography Quill Random Barkings S'Mary's World Shakers of Salt Software Development The Dog Whistler The Dogmat Sez Third Orders Thomas Aquinas Uncategorized Vikings at Dinos Woof Guide to Cinema Woof Guide to History Woof Guide to Literature Woof Guide to Obscure Catholic Music Woof Guide to Philosophy Woof Guide to Popular Music Woof Guide to Technology Woof Guide to Theology Words I Wish I'd Written Works For Me

Select a Month September 2016 August 2016 June 2016 May 2016 April 2016 March 2016 February 2016 January 2016 December 2015 November 2015 October 2015 September 2015 August 2015 July 2015 June 2015 May 2015 April 2015 March 2015 February 2015 January 2015 December 2014 November 2014 October 2014 September 2014 August 2014 July 2014 June 2014 May 2014 April 2014 March 2014 February 2014 January 2014 December 2013 November 2013 October 2013

TAKE THE

Religious Wisdom Quiz

Who was the Roman governor at the trial of Jesus?

Select your answer to see how you score.

Pilate Herod Caesar Alexander