In line two, the speaker says that she loves her beloved as deep and as wide and as high as her soul can reach, as though her soul is something she can expand or stretch out in order to encompass or even make room for more love. She employs a spatial metaphor, implying that her soul can take up a certain amount of space, as can her love. The speaker then describes the way her soul might feel around further than she can physically see, almost like reaching one's arms out for a light switch in the dark, reaching for the "ends of Being and ideal Grace." So, she stretches her soul out, out, as far as she possibly can, trying to find out just how far she can stretch it, to see if her love for her beloved extends that far, and it does. Where will her Being end? And will the Grace of her love extend the same amount? It does!