What does the speaker mean by "fearful symmetry"?

This line is within a larger question that the speaker poses in "":

What immortal hand or eye,

Could frame thy
fearful symmetry?

Within the
creation of the tiger is a much bigger question that centers around the essence of the Creator.
If God works as a craftsman to create every wonderful thing, does He then also work in
"symmetry" to create a counterbalance of darkness?

The perfect symmetry of a tiger then, its perfect form and shape, has a counterbalance:
It is capable of great devastation. The speaker is questioning whether both goodness and
darkness originate from the same Creator. If there is innocence (I often teach this poem in
conjunction with "The Lamb," which elicits this opposing image of God's creation and
is also written by Blake), then must there also be corruption? If there is beauty, must there
then also be fear?

The speaker provides no answers about
the "symmetry" of God's design but allows readers to discern this answer for
themselves.