it extends the phrasing of the rest of the sentence In proportion as he simplifies his life, the laws of the universe will appear less complex, and solitude will not be solitude, nor (will) poverty (be) poverty, nor (wil) weakness (be) weakness. Because he has established the pattern with Solitude, it is clear that he intends to say that Poverty will stop being poverty, because of the same thing that stops Solitude being Solitude. I don't fully understand the passage, it is a deep and subtle thought, that when one really understands the universe, so that everything seems really simple, then these things cease to exist as concepts in our minds.