'Sacred doctrine is a science. We must bear in mind
that there are two kinds of sciences. There are some which proceed from a
principle known by the natural light of intelligence, such as
arithmetic and geometry and the like. There are some which proceed from
principles known by the light of a higher science: thus the science of
perspective proceeds from principles established by geometry, and music
from principles established by arithmetic. So it is that sacred doctrine
is a science because it proceeds from principles established by the
light of a higher science, namely, the science of God and the blessed.
Hence, just as the musician accepts on authority the principles taught
him by the mathematician, so sacred science is established on principles
revealed by God.'