In this critical edition of Nicole Oresme's 14th-century treatise on atmospheric refraction, Oresme uses optics and infinitesimals to help solve this vexing problem of astronomy, proposing that light travels along a curve through the atmosphere, centuries before Hooke and Newton.

This comprehensive reference volume features essays by some of the most distinguished scholars in the field. Provides a comprehensive "who's who" guide to medieval philosophers. Offers a refreshing mix of essays providing historical context followed by 140 alphabetically arranged entries on individual thinkers. Constitutes an extensively cross-referenced and indexed source. Written by a distinguished cast of philosophers. Spans the history of medieval philosophy from the fourth century AD to the fifteenth century.

Natural philosophy encompassed all natural phenomena of the physical world. It sought to discover the physical causes of all natural effects and was little concerned with mathematics. By contrast, the exact mathematical sciences were narrowly confined to various computations that did not involve physical causes, functioning totally independently of natural philosophy. Although this began slowly to change in the late Middle Ages, a much more thoroughgoing union of natural philosophy and mathematics occurred in the seventeenth century and thereby made the Scientific Revolution possible. The title of Isaac Newton's great work, The Mathematical Principles of Natural Philosophy, perfectly reflects the new relationship. Natural philosophy became the 'Great Mother of the Sciences', which by the nineteenth century had nourished the manifold chemical, physical, and biological sciences to maturity, thus enabling them to leave the 'Great Mother' and emerge as the multiplicity of independent sciences we know today.

Superstitions are commonplace in the modern world. Mostly, however, they evoke innocuous images of people reading their horoscopes or avoiding black cats. Certain religious practices might also come to mind—praying to St. Christopher or lighting candles for the dead. Benign as they might seem today, such practices were not always perceived that way. In medieval Europe superstitions were considered serious offenses, violations of essential precepts of Christian doctrine or immutable natural laws. But how and why did this come to be? In Fearful Spirits, Reasoned Follies, Michael D. Bailey explores the thorny concept of superstition as it was understood and debated in the Middle Ages. Bailey begins by tracing Christian thinking about superstition from the patristic period through the early and high Middle Ages. He then turns to the later Middle Ages, a period that witnessed an outpouring of writings devoted to superstition—tracts and treatises with titles such as De superstitionibus and Contra vitia superstitionum. Most were written by theologians and other academics based in Europe’s universities and courts, men who were increasingly anxious about the proliferation of suspect beliefs and practices, from elite ritual magic to common healing charms, from astrological divination to the observance of signs and omens. As Bailey shows, however, authorities were far more sophisticated in their reasoning than one might suspect, using accusations of superstition in a calculated way to control the boundaries of legitimate religion and acceptable science. This in turn would lay the conceptual groundwork for future discussions of religion, science, and magic in the early modern world. Indeed, by revealing the extent to which early modern thinkers took up old questions about the operation of natural properties and forces using the vocabulary of science rather than of belief, Bailey exposes the powerful but in many ways false dichotomy between the "superstitious" Middle Ages and "rational" European modernity.

The Middle Ages is often viewed as a period of low intellectual achievement. The name itself refers to the time between the high philosophical and literary accomplishments of the Greco-Roman world and the technological advances that were achieved and philosophical and theological alternatives that were formulated in the modern world that followed. However, having produced such great philosophers as Anselm, Peter Abelard, John Duns Scotus, William of Ockham, Peter Lombard, and the towering Thomas Aquinas, it hardly seems fair to label the medieval period as such. Examining the influence of ancient Greek philosophy as well as of the Arabian and Hebrew scholars who transmitted it, The A to Z of Medieval Philosophy and Theology presents the philosophy of the Christian West from the 9th to the early 17th century. This is accomplished through a chronology, an introduction, appendixes, a bibliography, and hundreds of cross-referenced dictionary entries on the philosophers, concepts, issues, institutions, and events, making this an important reference for the study of the progression of human thought.

Based on scores of medieval manuscript texts and diagrams, the book shows how Roman sources were used in the age of Charlemagne to reintroduce and expand a qualitative picture of articulated geometrical order in the heavens.