first century, mediaeval civilization could hardly, after the collapse of
the crusades, have failed to degenerate as Roman civilization degenerated
after the defeat of Varus. Being more elastic, it began, under an
increased tension, to develop new phases of thought. The effort was indeed
prodigious and the absolute movement possibly slow, but a change of
intellectual attitude may be detected almost contemporaneously with the
fall of the Latin kingdom in Palestine. It is doubtless true that the
thirteenth century was the century in which imaginative thought reached
its highest brilliancy, when Albertus Magnus and Saint Thomas Aquinas
taught, when Saint Francis and Saint Clara lived, and when Thomas of
Celano wrote the _Dies Irae_. It was then that Gothic architecture touched
its climax in the cathedrals of Chartres and Amiens, of Bourges and of
Paris; it was then also that Blanche of Castile ruled in France and that
Saint Louis bought the crown of thorns, but it is equally true that the
death of Saint Louis occurred in 1270, shortly after the thorough
organization of the Inquisition by Innocent IV in 1252, and within two
years or so of the production by Roger Bacon of his _Opus Majus_.

The establishment of the Inquisition is decisive, because it proves that
sceptical thought had been spread far enough to goad the Church to general
and systematic repression, while the _Opus Majus_ is a scientific
exposition of the method by which the sceptical mind is trained.

Roger Bacon was born about 1214, and going early to Oxford fell under the
influence of the most liberal teachers in Europe, at whose head stood
Robert Grosseteste, afterward Bishop of Lincoln. Bacon conceived a
veneration for Grosseteste, and even for Adam de Marisco his disciple, and
turning toward mathematics rather than toward metaphysics he eagerly
applied himself, when he went to Paris, to astrology and alchemy, which
were the progenitors of the modern exact sciences. In the thirteenth