In the term "fearful symmetry," Blake refers to the problem of aesthetics or beauty. The Tyger is a beautiful animal. It has bright eyes, and it "burns bright" with intense energy. It has been carefully forged by an unknown craftsman in what is described as a blacksmith's shop. The creature is forged and "twisted" out of strong ingredients, such as molten iron and a mighty hammer.

Yet the beautiful Tyger is also "fearful" because it is a ruthless predator who uses its "symmetry"—it grace and balance and beauty—to ruthlessly destroy and devour other creatures. Why is this, the speaker wonders? Why is beauty (symmetry) used in an evil (fearful, frightening) way?

"Fearful symmetry" also harkens back to the companion poem to this one in Songs of Innocence, "The Lamb." What is the symmetry between a lovely, white, pure, innocent creature like a lamb, the symbol of Christ, who harms no one, and the lovely, lean, rippling, but fiercely predatory Tyger? Why at heart is there a seeming "symmetry" or balance between good and evil, compassion and predation? The speaker questions how or why a God could create a beautiful and gentle animal and a beautiful and cruel animal.

The speaker is thus asking, at heart, the often raised question of why evil exists and why it is so often compellingly "bright" and attractive. Unlike in "The Lamb," in which answers abound to explain the world, here there are no answers—only anguished questions inviting the reader to participate in pondering them.

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

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.

In order to grasp the meaning of the phrase "fearful symmetry" in "The Tyger" by William Blake, it's important to understand it in the context of the entire poem. At the end of the first stanza and again at the end of the overall poem, Blake asks the question, "What immortal hand or eye, dare frame thy fearful symmetry?" Blake was a Christian writer, and in this poem he wonders whether God, who created so much good, could have also created a creature of such deadly power as a tiger. The poem asks,

Did he smile his work to see?
Did he who made the Lamb make thee?

In these lines, "he" refers to God, and Blake wonders whether God would feel joy at the creation of the tiger, which, though visually beautiful, destroys and devours other creatures. "The Lamb" is symbolic of Jesus Christ (as well as referring to meek, innocent creatures), and Blake questions whether the same God who created Jesus Christ could possibly have created the frightening tiger.

The phrase "fearful symmetry" is a summation of the question that Blake poses, but does not really answer, in the poem. "Symmetry" means the beauty inherent in the excellence or perfection of proportion. The concept of symmetry would not normally be frightening. When Blake adds the adjective "fearful" to symmetry, he suggests something that doesn't fit and that cannot be explained. In other words, he questions the creation of evil by God, when God is supposed to create only beauty and perfection.

What Blake is trying to do here is convey the sheer awe and sense of wonder that the tiger inspires. The tiger is “fearful,” in that it induces fear in all who see it. At the same time, it has “symmetry” in its appearance, a sense of balance and proportion traditionally associated with objects of great beauty. So in other words, Blake presents the tiger as being scary and beautiful at the same time.

As well as being scary and beautiful, the tiger is also sublime. Its savage wildness cannot be neatly contained, or “framed,” as the poem has it. As the tiger emerges from the forests of the night, it isn’t subjected to any boundaries; this is real life, not a painting where the action can be framed. Not even God himself, the “immortal hand or eye,” can control or contain the tiger’s fearsome beauty, which takes on a life of its own.