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Physics and Metaphysics
in the Seventeenth Century
The seventeenth century was a period of such crucial and rapid change in outlook that we may justifiably speak of it as marking the birth of modern science. Two landmarks in the growth of the new science were Galileo's Dialogue (1632) and Newton's Principia (1687). The lives of these two persons also provide illuminating examples of the interactions between science and religion that are our concern. It was in the physical sciences that the new intellectual climate first captured the human imagination and became the basis for a new world view. To see the extent of the transition wrought, we will start by outlining some assumptions of the Middle Ages that were challenged in the seventeenth century. We look successively at "The Medieval World-Drama," "Galileo's 'Two New Sciences,'" and "The Newtonian World-Machine."
Our objective is to analyze how views of God and human nature were affected by the new methods of inquiry in science and the new scientific understanding of nature. We will indicate briefly the approaches taken by Aquinas, by Galileo, and then by Newton, to the following topics: (1) methods in science, (2) the character of nature, (3) methods in theology, (4) God's relation to nature, and (5) human nature. The final section of the chapter examines the positive contributions of religious thought to the rise of science and the major points of conflict.
In some cases, specific scientific theories, such as the Copernican theory that the sun rather than the earth is the center of the planetary system, seemed to conflict with traditional religiousideas. But science also influenced religious thought indirectly by calling philosophical assumptions into question, especially those in epistemology (analysis of methods of inquiry and theories of knowledge) and metaphysics (analysis of the most general characteristics of reality; see Glossary for definitions of frequently used specialized terms). We will be considering both direct and indirect influences of the new science on views of nature, God, and humanity.
These chapters of historical background do not try to describe all the complex factors in the growth of modern thought in either science or religion. In each field new ideas were the product, not of isolated individuals, but of communities of inquiry within wider cultural contexts. The social history of both science and religion is as important as an account of "great scientists" or "important theologians." However, the discussion of a few pivotal figures in their social contexts can serve to illuminate the origins of contemporary issues.
Amid the rich diversity of the Middle Ages, Thomas Aquinas (1225-1274) stands out as the most systematic and influential medieval author. His synthesis of Christian theology and Aristotelian philosophy articulated a distinctive approach to both science and religion that dominated Western thought until the seventeenth century. Let us consider his views on each of our five topics.
1. Methods In Science: Explanation By Purposes
During the 1950s and 1960s, several widely read books by historians of science portrayed the radical character of the "scientific revolution" of the seventeenth century and claimed that the Middle Ages made no substantial contributions to science.1 More recently, specialists in the history of medieval science have made detailed studies of particular people and topics. They insist that medieval authors must be examined in the context of their own times and that significant advances were made in medicine, technology, and physics. They point to continuity as well as discontinuity between medieval and early modern science. For example, Galileo's concept of inertial momentum had a precursor in the writings of jean Buridan and Nicole Oresme at the University of Paris in the fourteenth century, namely their idea of "impetus" as the cause of continuing motion.2
Yet even these recent authors acknowledge that medieval science was carried out within an Aristotelian framework with goals very different from those of Galileo and his successors. Medieval writers were primarily interested in the logical relationships among ideas, and only secondarily were they interested in testing hypotheses by experiments. I will argue that modern science really does represent a revolution in methods of inquiry, so that ideas with forerunners in earlier centuries were used in a new way. Greek science was recovered when the writings of Aristotle were translated from Arabic in the thirteenth century. From 1250 to 1650, Aristotle was the core of the curriculum in the universities of western Europe. Science was not an autonomous profession but a branch of philosophy, and Aristotle's Physics was widely read and discussed and challenged, even though its basic assumptions were still accepted.
For what type of explanation of an event should one search? To what sort of questions about nature is it most important to seek answers? Aristotle sought explanations in terms of the true form or intelligible essence of an object and the purpose it fulfills. Why do objects fall? For Aristotle and his followers, motion is explained by the tendency of each thing to seek its own natural resting place. The "natural place" of fire is up, and that of earth is down. The end of the motion--in the sense both of terminus and of purpose--was of more interest than the intervening process. Why does an acorn grow? To become an oak. Why is there rain? To nourish plants. Causality is described by future goals ("final causes") and innate tendencies ("formal causes"), not just by the effects of past events ("efficient causes") acting on objects in the present ("material causes"). The future goal need not be consciously entertained by an entity (for example, an acorn) but is built into its structure so that by its own nature it achieves the fulfillment of the end appropriate to its kind by the expression of form through matter.3
Attention was directed to the final end and not to the detailed process of change from moment to moment. The behavior of each creature follows from its essential nature.