The idea that 17th century thinkers somehow developed an "original concern for rationality and the claims of Reason," says Toulmin, is "misleading":
Rather than expanding the scope for rational or reasonable debate, 17th century scientists narrowed it. To Aristotle, both Theory and Practice were open to rational analysis, in ways that differed from one field of study to another. He recognized that the kinds of argument relevant to different issues depend on the nature of those issues, and differ in degrees of formality or certainty: what is "reasonable" in clinical medicine is judged in different terms from what is "logical" in geometrical theory. Seventeenth-century philosophers and scientists, by contrast, followed the example of Plato. They limited "rationality" to theoretical arguments that achieve a quasi-geometrical certainty or necessity: for them, theoretical physics was thus a field for rational study and debate, in a way that ethics and law were not. Instead of pursuing a concern with "reasonable" procedures of all kinds, Descartes and his successors hoped eventually to bring all subjects into the ambit of some formal theory: as a result, being impressed only by formally valid demonstrations, they ended by changing the very language of Reason—notably, key words like "reason," "rational," and "rationality"—in subtle but influential ways.We could add, as another methodological fallacy introduced by the rise of scientific materialism, the idea, not only that rationality encompasses only the formally valid, but that it includes only the empirically verifiable (the tradition that comes from Bacon, as opposed to Descartes). And of course the irony here is that the idea of strict formal demonstration and empirical verifiability are largely conflicting methodologies.
To say the the 17th century was a time in which Reason was freed from the shackles of Medieval superstition is one of the founding myths of scientism. "Clearly," says Toulmin, "it is time to give up any assumption that the 17th century was a time--the first time—when lay scholars in Europe were prosperous, comfortable, and free enough from ecclesiastical pressure to have original ideas; and it is also time to reconstruct our account of the transition from the medieval to the modern world on a more realistic basis."
For anyone to call the Middle Ages—the age of Peter Abelard, Albert the Great, Thomas Aquinas, and Duns Scotus—is to betray a basic ignorance of medieval history and thought. In fact, the Middle Ages was perhaps the great age of logic. Alfred North Whitehead goes so far as to say that the revolt of Galileo was far from a revolt into reason. "On the contrary," says Whitehead, "it was through and through an anti-intellectualist movement."
The Middle Ages, Says Whitehead, "was the age of faith based upon reason. In the later period, they let sleeping dogs lie: it was the age of reason based upon faith."