These three words have been separated from the rest of the line by "--". This is to make sure the reader notices the importance of these words and what they mean to the overall theme of the poem. This line occurs directly after Kipling has just said, "Yours is the Earth and everything that's in it". Owning the entire earth and everything in it is a very Imperialistic thought, especially since some British citizens believed they were the greatest example of human evolution. And Imperialist would extremely want to own the Earth and everything that’s in it, making him or his country almost God. But then Kipling ends the poem saying "--which is more-- you'll be a Man, my son!" Here Kipling offers a different piece of advice than his usual Imperialist thought. He is telling the reader that containing the traits he has just described is more important than owning the earth. Basically saying that being a man in principle is more important than owning anything possible. This last line is the line that shows how "IF--" is not meant to be Imperialist rhetoric, but instead advice on how to live a good life.