Why does Equality want for the first time to know what he looks like? What is the significance of this action?

We stretch out our arms. For the first time do we know how strong our arms are. And a strange thought comes to us: we wonder, for the first time in our life, what we look like. Men never see their own faces and never ask their brothers about it, for it is evil to have concern for their own faces or bodies. But tonight, for a reason we cannot fathom, we wish it were possible to us to know the likeness of our own person.

Equality's discovery has made him wonder about himself and his own abilities, he marks the differences between himself and his brothers. For the first time, he not only thinks of himself as an individual..... he sees himself as an individual.