Cutting Between Soul and Spirit

In my daily Bible reading I read Hebrews 4:12. It says, 

For the word of God is alive and powerful. It is sharper than the sharpest two-edged sword, cutting between soul and spirit, between joint and marrow. It exposes our innermost thoughts and desires.

I almost glossed over these verses. The idea is so familiar. The word is the living word of the living God.  But then I noticed something.

This verse says that God's word cuts between soul and spirit. Soul and spirit usually mean the same thing. It seems odd to say that God's word cuts between them. But the words are not always the same. The Holy Spirit, God's voice inside of us, is never called a soul. That still doesn't tell me what this verse means, but here's what this verse means for me: God's word helps us distinguish between God's voice (the spirit) and our own voice (the soul). Just as joint and marrow are both good and necessary, and so are God's voice and our own individual voices, but it's important to see the difference.

The verse also says that it's God's word which exposes our innermost thoughts and desires. Not God, but God's word. This verse tells me that God's word exposes my innermost thoughts and desires to myself. God already knows them and, through His word, reveals them to me.