From the introduction to my medieval philosophy class:
There are two methods to study a chronological period of philosophy: one is primarily historical, and engages the thought of the time insofar as it is effected by political or social changes, such as the fall of the Roman Empire (beginning around 376ad with the Gothic invasions) and the dissolution of Catholic Christendom (beginning in 1517ad with the Protestant Reformation); the other is to consider it primarily philosophically, i.e., as united by some common idea or concern, or a set of ideas; as the development of a particular way of thinking. The historical method is a valid approach—but only as a historical sociology which, while it may give clues as to the motivations for the development of the philosophical ideas, cannot explain that development itself, let alone the ideas. We cannot understand the history of philosophy without understanding the philosophy itself. Thus, even the determination of the period’s duration, its beginning and end, will be somewhat arbitrary and lacking in a precise reason for its establishment: in other words, can we say that some philosophy is medieval because it falls within certain years? Contrariwise, the philosophical consideration of a period of thinking, which demands a familiarity with the historical context, reveals the prevailing concern which is the underlying source of unity by means of which we can validly distinguish one historical period of philosophy from another. In other words, we are looking primarily for an idea or a set of concerns that makes philosophy “medieval”, not a period between two dates.
This method of distinguishing periods of philosophy is not, however, to say that anything which touches upon the defining characteristics of such a period must be considered to belong to that period. In other words, it is not just the idea or set of concerns which defines a philosophical period. The extra-philosophical considerations of the political, geographical, and cultural landscape enter into a kind of complex and unique web with the philosophical ideas themselves, to create an unrepeatable epoch. While the dates do not define a period of philosophy, they do incidentally contain such a period. The philosophy we practice today cannot be “medieval” any more than it can be “ancient”. While Etienne Gilson, Armand Maurer, Joseph Owens, and many other Catholic philosophers of the 20th century have taken up the problems and ideas of Augustine of Hippo, Thomas Aquinas, John Duns Scotus, and William of Ockham, we would by no means consider Gilson, Maurer, and Owens to be medieval philosophers. Though some may try, we can never displace our own philosophical considerations into a previous point in history and remain genuine philosophers.
For what is philosophy? Etymologically, of course, it is the love (philo-) of wisdom (sophia). To the ear of today, this may sound rather poetic; and indeed, philosophy is typically classed among the “liberal arts”—that is, the roundly-humanistic endeavors which serve to make gentlemen and women—as opposed to the “sciences”—the empirically-based and experimentally verified researches which produce so-called “objective” knowledge: that is, data, facts, indisputable truths. This latter branch on the tree of study, empirical science, which is distinguished by the scientific method that was developed principally in the 17th century (and widely attributed to both Rene Descartes and Francis Bacon, though its roots go back much further), is typically considered to be more reliable and more useful in its own right than the liberal arts, which may help to make a man more civil, but which cannot put him on the moon or keep his food cold. This distinction between the liberal arts and the sciences, however, is often mistaken for being a distinction between, on the one hand, that which is concerned with matters of opinion and, on the other, that which is concerned with matters of fact. What is, in reality, at the root of the distinction is the method of inquiry: for science in the modern sense conducts its inquiry through experimentation, to be sure, but these experimentations and the subsequent classification of the data are principally through mathematical abstractions to some degree or another. The biological sciences, certainly, do not rely as heavily upon mathematics as do either classical or quantum physics; but oftentimes, whether or not something is to be considered a science is dependent upon whether or not it can demonstrate its conclusions in a mathematically verifiable medium, such that experiments can be quantified and subsequently repeated. The results of experiments in all such sciences are recorded in terms of quantified data. What is furthermore common to these sciences is that they make use of some specialized instrumentation—which includes mathematical constructs (both the numerical and the geometrical), hypotheses, pre-ordained systems of classification (such as kingdom, phyllum, etc.), as well as material instruments such as telescopes, microscopes, fMRI (functional magnetic resonance imaging) machines, and particle colliders—to carry out their researches. In other words, they are studying some specified aspect of the universe through some specific medium or media, through a kind of instrument.
Contrariwise, philosophical speculation—along with studies of literature, history, theology, and other such subjects—while it oftentimes (though not always) constricts itself to a specific aspect of the universe, that is, to considering certain objects, does so without requiring some specific restriction of method. Every part of the universe is thus open to this general mode of inquiry, according to the interpretative lens of common experience—there are no specific methods, and while there are specific terms which come to be identified as belonging, for instance, to some philosophical system (such as “substance”) or school of literary theory (“trochaic inversion”), these terms describe the things themselves; they are translatable, and, in a sense, universal.
Medieval thinkers, however, did not distinguish between these two modes of inquiry, between science as it is understood in the modern sense, and what are today liberal arts. Natural sciences as we know them today had neither their own distinctive methods nor their own distinctive monikers: Scholastic philosophers classified them all under the generalized science of “physics,” according to the system of Aristotle. It was not until Aristotle became widely available in medieval Europe, through the influence of Islamic philosophers, that natural sciences became a prevalent concern of medieval thinkers. Philosophical speculation in Europe prior to the advent of Aristotelian texts was principally aimed not at understanding the world around us, but rather at making accessible and knowable the teachings of faith—often with confused and confusing (sometimes disastrous) results, though in some cases with exceptional success. Prior to the Scholastic period, medieval philosophy was much more concerned with the moral life.
While the successes of medieval philosophy are rare, they are no more rare than any other period in history—and, absolving their failures with regards to natural science, it seems quite fair to say that it is possibly the most successful period in the history of philosophy, insofar as ideas were developed and advanced, rather than simply batted back and forth between adversaries. Though only a few names stand out as presenting true breakthroughs in thought, or putting forth a remarkable and holistic approach to philosophy, there are numerous contributions from lesser-known thinkers; the years between Thomas Aquinas and William of Ockham, for instance, was not given over to void; nor from Ockham to John Poinsot. The great masters had their disciples, who sought to expand upon and clarify the doctrines of their teachers, and so up sprung many “schools” of thought: an Augustinian school, the Lombardians, the Victorines, the Thomist school, the Scotists, the Ockhamites, and so on.
Despite their various differences as to the meanings of words or the realities signified by those words, each of these schools engaged in a common inquiry, a common inquiry which we take for the unifying theme for our study of medieval philosophy: namely, that if theology is the science which reads from the book of revelation, and philosophy is the science which reads from the book of nature, how are these two books to be understood in relation to one another? What is the relationship between faith and reason?
The General Notion of Sign
As will become clear over this course, this project—the reconciliation of the books of revelation and nature—faces many challenges. There are many difficult questions, particularly when it comes to human understanding and the nature of the soul in relation to both the natural and the supernatural, to which the answers are opaque and require difficult thinking. What enabled the medievals to progress in their theoretical inquiry, though they were not likely aware of its importance until near the end, was the general notion of the sign. Whereas ancient philosophy recognized the importance of natural signs—where there’s smoke, there’s fire, habitual paleness indicates a health problem, birds flying south signals the approach of winter—it was not until St. Augustine, the first of the truly medieval philosophers, that there was a general notion of the sign, which includes not only natural signs but also the conventional signs of societal interaction, as well as the signs by means of which the mind is able to attain and develop knowledge. The importance of this doctrine was undoubtedly lost on Augustine, as many of the developments following his general notion took place centuries later. Nevertheless, the insight that signs are not restricted to the relationships between “things”, i.e., the beings which exist as they are independently of any cognitive activity, but exist also within the cognition-dependent beings such as words remains an invaluable step forward in philosophical progress.
Christianity undoubtedly had a profound impact on Augustine’s consideration of the sign—after all, the doctrine is most clearly laid out in De magistro (On the Teacher, who, for Augustine, is Christ) and in De doctrina Christiana (On Christian Teaching). Interpretation of Scripture was a major difficulty with which the Church has always been faced, and one which has grown exponentially the more that the Bible has been translated into other languages—indeed, during Augustine’s own lifetime, St. Jerome was working on his translation into Latin (which was also something of a revision of the older Latin text), the language of Augustine, who famously loathed the Greek tongue. This need to clarify the meaning of Scripture, of providing a means to interpret the text correctly, does seem to mandate a contemplation of the nature of words, how they signify, and especially how they signify differently from natural signs. Moreover, Christ Himself is named in the beginning of the Gospel of John as the Word: In principio erat Verbum, et Verbum erat apud Deum, et Deus erat Verbum: In the beginning was the Word, and the Word was with God, and the Word was God. He was in the beginning with God. All things were made through Him, and without Him came nothing that has come to be. These opening passages from John have been the subject of much commentary by Christian thinkers, not the least of which are Sts. Augustine and Thomas Aquinas; and indeed, each reflected greatly upon the signification of the Word and the words.
 Though we most certainly do consider them historians of medieval philosophy, heavily influenced by medieval philosophy, and, though it is a somewhat dubious word, “medievalists.”
 Oftentimes, however, with too much zeal: many attributes of the so-called scientific method have persisted since at least the time of Aristotle, and may be found in Albertus Magnus, Thomas Aquinas, and Roger Bacon.