Why are there so many unanswered questions in "The Tyger" by William Blake?

To answer this question we need to be aware of the subject of
the poem. In this poem the speaker is admiring the startling energy of the Tiger that he sees and
can only wonder whether it is demonic or godlike. Again and again, throughout the poem the speker
asks the tiger who its creator was. The implied answer that is never actually given to us is that
it can only be either God or the devil. Note how this questioning operates in stanza
three:

And what
shoulder, and what art,

Could twist the sinews of thy
heart?

And when thy heart began to
beat,

What dread hand? and what dread
feet?

The focus is on the identity of
the creator of the tiger, and the relentless questioning that goes on throughout the poem only
serves to highlight the uncertainty of the speaker. Such an energy, such a force, could only be
the creation of two people, and it is unsure which we can look to.