Corinthians 2:11 - “No one can know a person's thoughts except that person's own spirit, and no one can know God's thoughts except God's own spirit.”  Just as our life essence, our spirit, our soul, dwells within our physical body, God's life essence, His spirit, His Self, dwells within Him.  Just as our spirit and our soul cannot be divided one from the other, neither can God's spirit, His Self, be divided.  God is Spirit, Spirit is God.  The word which we render as Spirit is Pneuma in the Greek, and Ruach in the Hebrew - wind; by resemblance, breath.  The Spirit of God is the breath, breathings, life force which is God.  Not of God, but is God.  The Spirit of God, is both the Father Himself, and Jesus Himself.  The Father is the Spirit; Jesus is the Spirit.  The Spirit is the Father, the Spirit is Jesus.  The Spirit is not an essence within which the Father and the Son have their existence, they are that essence, the Spirit is they.