Johannes Kepler, who lived from 1571 to 1630, was a natural philosopher who thought of himself as using mathematics as the language.
From a very modern point of view, one could highlight Kepler’s epistemological thought in terms of four different items: realism; causality; his philosophy of mathematics; and his own particular empiricism.. Realism is a constant and integral part of Kepler’s thought, and one which appears in sophisticated form from the outset. The reason for this is that his realism always runs parallel to his defense of the Copernican worldview. Despite Kepler’s criticism of Aristotle regarding causality, this aspect can actually be considered the realization in the field of astronomy of the old Aristotelian ideal of knowledge: “knowledge” means to grasp the causes of the phenomena. Besides, Kepler produced original contributions to the theory of logarithms and, above all, within his favorite field, geometry. And last, epistemic discipline: abstract claims must be verified by actual experience. In this way, Kepler combined his belief in the knowability of the surrounding world with the rigor of the scientific and mathematical method.
Kepler’s religious beliefs played a central role in his research. Since the Creator is absolutely rational, creation inherits a rational form accessible to creatures made imago Dei; the studies of geometry is therefore not merely a handy human tool but a key to being and rationale of God: creation inherits a rational form accessible to creatures made in the image of God; the studies of the Creator. Kepler regarded mathematics as a bridge for knowledge: mathematical objects are not just abstract symbols but solutions to explaining the well-ordered universe. This creates a simple but beautiful, balanced relationship,connecting the different parts of nature. And this viewpoint, like a law, creates a harmony among mathematics, metaphysics, and his religious beliefs. Throughout his life, Kepler was a profoundly religious man. All his writings contain numerous references to God, and he saw his work as a fulfilment of his Christian duty to understand the works of God. Man being, as Kepler believed, made in the image of God, was clearly capable of understanding the Universe that He had created. Moreover, Kepler was convinced that God had made the Universe according to a mathematical plan, we have here a strategy for understanding the Universe.
His empiricism is equally impressive when it comes to error analyses. Long before modern error analysis, he has his own set of methods to do error analyses. To be noted is that, as Jardine (2005, p. 137) has pointed out, the modern scientific realist departs from a real independent world, while Kepler’s notion of truth presupposes that neither nature nor the human mind are independent of God’s mind (Jardine 2005, p. 137).
While Kepler was working on his Harmony of the World, his mother was charged with witchcraft. He enlisted the help of the legal faculty at Tübingen. Katharina Kepler was eventually released, at least partly as a result of technical objections arising from the authorities’ failure to follow the correct legal procedures in the use of torture. However, Kepler continued to work. In the coach, on his journey to Württemberg to defend his mother, he read a work on music theory by Vincenzo Galilei, to which there are numerous references in The Harmony of the World (Boner,2016). He folded the ideas of music theory into his broader project on harmony—an emblem of his conviction that rational order spans nature, number, and sound alike.
Kepler could also be strikingly practical. He had always been keen on devices—including a water-pump design he tried to patent—because philosophy, for him, had traction in the world. In that spirit, he recast the scholar’s vocation: the philosopher of nature seeks simple, intelligible structure by marrying geometry, cause, and disciplined observation—and lets reality, not rhetoric, have the last word.
Bibliography:
Jardine, N. The Many Significances of Kepler’s Contra Ursum. 2005.
Boner, Patrick. “Ulinka Rublack, The Astronomer and the Witch: Johannes Kepler’s Fight for His Mother.” Early Science and Medicine, 2016.