Kepler largely believed in the idea of the human mind being capable of understanding God’s plan and the divine way in which he creates the universe and allows it to run. Contrary to many other natural philosophers of his time, he strongly used empiricism and a posteriori knowledge to understand what God created, although he does use more philosophical speculation to implement God into his discoveries. This often included lots of observations and data analysis. In Astronomia Nova, for instance, Kepler largely uses the meticulous data from Tycho Brahe regarding Mar’s orbits to do calculations and come up with conclusions about the orbit of mars. Of course, these conclusions which he came to mathematically and with data were ultimately tied into his theological beliefs and how God’s power and presence is felt in the geometrical shapes which make up the planets and cause their orbits. Copernicus, whose model Kepler largely tried to prove, proposes the sun to be the center of the universe about which all planets revolve in circular orbits. Kepler largely spent his career trying to prove mathematically that the sun is the center of the universe, that the planets move in elliptical not circular paths yet are harmonious and interdependent on one another and the sun for their orbit and speed. Again, he uses his theological background to implement a more spiritual aspect on top of his empirically based causal reasons for planetary motion to help philosophically justify some of the harmonious qualities of the solar system.
It is important to note that during this time, the heliocentric theory very heretical and not accepted by any church institution as the bible views the universe as geocentric. It was very common at the time to accept the Ptomelaic view of the solar system which was more biblically accurate. Therefore, Kepler’s teacher who knew of the Copernicus’ heliocentric model taught Kepler this theory in private, and Kepler spent much of his career proving this model. Not only was Kepler proving something quite heretical, but as a religious person he still placed God in the structure of the universe, and focuses on how the mathematics of how the heliocentric model and harmonic nature that lies within it work to show God’s divine creation in the geometric qualities of the planets of the solar system. Additionally, this idea of planets moving harmoniously relate much to music and the harmony of sound, which in man made music reflects the harmony of the celestial bodies.
Kepler’s model of the solar system included planets which revolved around the sun and were made up of Platonic solids. These solids made up the polyhedra which Kepler believed is what make up the planets in our solar system and account for their motions in regards to the sun. This geometrical language, which Kepler said most would be acquaintance with at the time, is language which God used to make up the universe that humans can understand, saying that “God, in creating the and arranging the spheres, had in view the five regular solids of geometry,” with each planet having fixed motions and proportions in their shapes as well. (Kepler, Mysterium Cosmographicum) Therefore, it is the language of geometry which God uses to create the universe as we know it, and it is only calculations from data that Kepler uses to get to the point of knowing this truth about God. The idea of the polyhedral shape that make up the planets is also accountable as a contributing final cause of the nature of these planetary motions, and answers in a less empirical and more philosophical way as it is geometrical shapes that guide the distance and motion of these planets, and it is God who is the creator and designer of said shapes.
On par with Kepler’s unusually strong belief in empiricism to find truths, something not as common among natural philosophers, especially rationalists, were his laws of planetary motion. Although they were not entirely seen as laws at the time, they were revolutionary in how they have affected science and astronomy moving forward. In his Astronomia Nova, Kepler discovers the first two laws of planetary motion, much of which disproves many previously held ideas regarding the planets relationship with the sun, especially in the heliocentric model of the solar system. Kepler proves through meticulous calculations from precise measurements that the paths of the planets move irregularly, and that the sun actually affects the velocity of the planet at a given position in its orbit. Due to the elliptical path of the planets and the fact that the sun is not a passive central object like in Copernicus’ model, but one that influences the motion of the planets depending on the planet’s distance from the sun. The speed of a planet’s motion at a given point in its orbit varies as the path is elliptical and its distance form the sun differs at different points in its orbit. This entire process of finding truths about the universe was done to only further prove Kepler’s theological and spiritual ideas about the universe due to its harmonious and interdependent nature. Kepler states that “God himself served as his own model in creating the world,” and that geometry largely existed alongside God and therefore allowed these same harmonic and divine principles that regulated the universe to be felt at the human level as well. (Kepler, Harmonice Mundi) However, it was later in his career that Kepler reviewed his idea of a soul like power guiding planetary motion, like in Copernicus’ model, and concluded that that way of thinking about the cause of planetary motion was incorrect. He began to view the universe, due to his empirical understanding of it, as a mechanical work where the size and relative distance of two bodies had an effect on one another. He particularly focused on the idea of a force influencing the the velocity of a planet when placed closer or further away from the central body, the sun. This is all supported through calculations showing the reduced velocity of a planet when found to be further away from the sun, suggesting that the sun has a force like property that influences the planets’ velocity. This would only be speculated by Kepler and only later proven by Newton through his theory of gravity. However, Kepler still believed in God’s influence over the motion of the universe through the geometrical shapes which make up the planets.
In conjunction with Kepler’s focus on the astronomical harmonies that connect the solar system is his connection of this nature to harmony that exists on earth. In his Harmonice Mundi, he connects this harmonic relationship of angular speeds of planets and their distances from the sun with the harmonic relationship of notes in music. He states that the angular speed of the planet Earth from the sun is a ratio of 16:15, which in musical terms means that “Earth sings Mi-Fa-Mi, so we can gather ever from this that Misery and Famine reign in our habitat.” (Kepler, Harmonice Mundi) It is evident that this connection of harmony between the universe and humans can only be created through the God’s cosmological design. Also described in Harmonice Mundi is Kepler’s third law, one of his most famous and influential discoveries that only further manifested the idea of the harmonic nature of the universe and its relation to God. The mathematical proportion between planets’ distances from the sun and their orbital periods that this law states only provided further evidence for the interdependence of the planets and the sun and Kepler’s idea of harmony that connects us humans with a much larger harmony that God uses to design the universe.
Glossary:
Copernicus: Heliocentric model: This model of the universe, designed by Nicolaus Copernicus, places the sun at the center of the universe, and that all the planets including the earth will revolve in circular orbits around the sun. The sun is viewed here as a passive object and did not influence the motion of the planets.
Polyhedra: A shape which has many faces, and is made up of the 5 Platonic solids. It is this structure which makes up the planet and accounts for much of their motion from Kepler’s more a priori philosophy of the universe
Sources Used:
Di Liscia, Daniel A. “Johannes Kepler.” Stanford Encyclopedia of Philosophy, Metaphysics Research Lab, May 2011, plato.stanford.edu/entries/kepler/. Accessed 11 Oct. 2022.
Kepler, Johannes. Astronomia Nova. 1609.
Harmonices Mundi. Linz, 1619.
Mysterium Cosmographicum. Tübingen, 1597.