On page 289 of the 610 pdf of the Urtext of A Course In Miracles Jesus states "The only part of your mind that has reality, is the part that links you still with God."

In this text Jesus is referring to the Holy Spirit which he says is a combination of God and our Higher Self. It is sort of like a telephone line. This is why we want to follow the Holy Spirit and embrace the atonement now so that we may exit the state of confusion humanity and the Whole Sonship which includes all that is in any material form (including spirit and other dimensions) have manifested through the error that separation from God, which is all that IS, is possible.