The last stanza of the "The Tyger" is almost identical to the first. What is the significance of the one word changed in the last stanza?

In the first stanza, the speaker is asking if
something could be done, and in the last stanza the speaker is elevating that
if to a who would dare tostatement.  There is
more fear and emotional weight in the last stanza than in the first.  Blake has built
the poem up to this final line.  The poem is filled with very fearful images of the
power of this tyger who has burning eyes like fire and who has dread hands and dread
feet which can hammer, chain, smash and grasp its prey.  The ultimate question of the
poem comes in the 5th stanza when the speaker asks, "Did he smile his work to see? / Did
he who made the Lamb make thee?"  This poem is asking if the immortal hand that created
the fierce tyger is pleased with his work and is it the same immortal hand that created
an opposite creature like the Lamb.  This poem, and its opposite poem, "The Lamb" both
come from Blakes Songs of Innocence and Songs of
Experience.  These collections of poems explore the innocence of the world or
the experience of the world.  The innocent poems suggest optimism, hope, faith, and
simplicity.  The experience poems suggest pessimism, fear, and harsh reality.  There are
sweet things in this world, like Lambs (suggestive of  faith in Jesus Christ) and there
are animals to be feared, like the tyger, used metaphorically to suggest a harsher world
of experience.