The works of the freethinker Averroes (twelfth century) which were based
on Aristotle’s philosophy, propagated a small wave of rationalism in
Christian countries. Averroes held the eternity of matter and denied the
immortality of the soul; his general view may be described as pantheism.
But he sought to avoid difficulties with the orthodox authorities of
Islam by laying down the doctrine of double truth, that is the
coexistence of two independent and contradictory truths, the one
philosophical, and the other religious. This

[69] did not save him from being banished from the court of the Spanish
caliph. In the University of Paris his teaching produced a school of
freethinkers who held that the Creation, the resurrection of the body,
and other essential dogmas, might be true from the standpoint of
religion but are false from the standpoint of reason. To a plain mind
this seems much as if one said that the doctrine of immortality is true
on Sundays but not on week-days, or that the Apostles’ Creed is false in
the drawing-room and true in the kitchen. This dangerous movement was
crushed, and the saving principle of double truth condemned, by Pope
John XXI. The spread of Averroistic and similar speculations called
forth the Theology of Thomas, of Aquino in South Italy (died 1274), a
most subtle thinker, whose mind had a natural turn for scepticism. He
enlisted Aristotle, hitherto the guide of infidelity, on the side of
orthodoxy, and constructed an ingenious Christian philosophy which is
still authoritative in the Roman Church. But Aristotle and reason are
dangerous allies for faith, and the treatise of Thomas is perhaps more
calculated to unsettle a believing mind by the doubts which it
powerfully states than to quiet the scruples of a doubter by its
solutions.

There must always have been some private