The period from the middle of the tenth to the beginning of the thirteenth century not only witnessed a great number of changes affecting nearly every important field of human experience; but the changes were most subtly connected one to another. Independent in their origins, they became interdependent in their effects; and their interdependence was not of the simple sort which is adequately represented by the familiar analogy of threads uniting to form a pattern. For the threads did not merely cross and recross. It would be more exact to describe them as continually untwisting into their constituent fibres which then reappear in fresh combinations. And they did not just exist side by side; they altered one another's substantial character by their proximity. Moreover—and this perhaps is the circumstance which makes the period most difficult to clarify—the renaissance following from these new departures failed to come to that brilliant fruition which an observer of its first beginnings would have naturally expected. Every change that occurred generated such a vigorous opposition that the innovators had to come to terms everywhere with those who wished to preserve the status quo. So there was not a single clear-cut line of growth. There were only a series of false starts. Tendencies which were later to become dominant in the fifteenth and sixteenth centuries showed themselves for the first time. But they met with hostility and were aborted. Nothing developed freely. Every thesis was countered by an immediate and more powerful antithesis.

The new age owed its progressive character to a variety of circumstances. Life was generally more settled. The impetus of the great migrations had worn itself out.