She explains the order established by Providence by force of which
created beings seek their natural habitat, earthly things being
attracted downward, spiritual entities being drawn upward irresistibly
if they do not oppose this innate inclination to good. "It is as natural
for a man purged of all evil to ascend to God," she declares, "as it is
for a stream from a mountain height to fall into a valley."

Very shortly after this, the first stage of the celestial journey is
reached. "Direct thy mind to God in gratitude," she said, "who hath
united us with the first star." "Me seemed a cloud enveloped us, shining
dense, firm and polished like a diamond smitten by the sun. Within
itself the eternal pearl received us, as water doth receive a ray of
light, though still itself uncleft." This is the Heaven of the Moon, the
planet farthest removed from the Empyrean and therefore the sphere where
not only motion but also beatitude are least in the heavenly bodies. The
sphere of the Moon, indeed with those of Mercury and of Venus, is held
by Dante's cosmography to be within the shadow cast by the earth.
Consequently, the spirits in those three lowest Heavens are represented
as less perfect than those in the higher spheres, because in the moral
sense the shadow of earth fell upon their lives making them imperfect
through inconstancy, vain glory or unlawful love.

In the Heaven of the Moon a long disquisition is carried on by Beatrice
in explanation of Dante's question as to why there are spots on the
moon. It is very likely that this matter of apparent irrelevance in the
heavenly realms is introduced here at the very first stage of the ascent
to give the poet the opportunity of proclaiming that the first thing one
must learn in his passage heavenward--even if this is to be understood
in an allegorical sense--is that the laws of the laboratory are not the
_rationale_ of the heavenly world and that to employ them to explain the
supernal is to violate the very science of these laws, in an
application of scope to which in their very nature they protest. This
point of seeing natural causes for the unexplainable phenomenon of
Heaven and especially of relying upon the testimony of the senses is
soon brought out by Beatrice reproving Dante for thinking that the
spirits whom he now sees are only reflections of the human face:

"Marvel thou not," she said to me, "because
I smile at this thy puerile conceit,
Since on the truth it trus