Where you are not, we have naught
Nothing good in deed or thought
Nothing free from taint of ill
Sine tuo numine
Nihil est in homine
Nihil est innoxium
Here, the Latin is much simpler and the English has to dance around with a bit more flair to fill the same syllable count. Remember of course that the Church sings her prayers, which in itself reflects the holy nature of prayer, of superfluous beauty spent for God's glory.
The Latin really just says, "Without you [oh deity], nothing is in man, nothing is freely innocent." The paradox is that God who is omnipresent can be excluded from souls by the very will given to the souls by the omnipotent God.
It seems that the root sin of humanity is pride: we think we are something when we are nothing. And this prayer says it plainly: we are nothing without the presence, the life breathed by the Holy Spirit. I'm not much of a linguist, nor am I much of a philosopher, but it strikes me as interesting to meditate on the phrase "nihil est in homine" -- nothing is in man. "Is" generally refers to the existence of something, while "nothing" of course is about the lack of something. Perhaps this drives at the God-shaped hole we all have within us, this having-been-created-for which we need to discover so that our calling out to God means something to us. It's this sense that I don't know who I am without You. And an existence that doesn't make sense to myself is unbearable, so I must seek so that I have peace.
We are designed for communion with God. In that communion, we experience the flow of freedom and innocence through us, which is the Spirit of God living through us. So today's chunk of this prayer expresses awareness of the depth of our need. Our human identity depends on our union with the Holy Spirit.