The term mind is used to represent the activating agent of spirit, supplying its creative energy. When the term is capitalized it refers to God or Christ (i.e. the Mind of God or the Mind of Christ). Spirit is the Thought of God which He created like Himself. The unified spirit is God's one Son, or Christ.
In this world, because the mind is split, the Sons of God appear to be separate. Nor do their minds seem to be joined. In this illusory state, the concept of an "individual mind" seems to be meaningful. It is therefore described in the course as if it has two parts; spirit and ego.
Spirit is the part that is still in contact with God through the Holy Spirit, Who abides in this part but sees the other part as well. The term "soul" is not used except in direct biblical quotations because of its highly controversial nature. It would, however, be an equivalent of "spirit," with the understanding that, being of God, it is eternal and was never born.
The other part of the mind is entirely illusory and makes only illusions. Spirit retains the potential for creating, but its Will, which is God's, seems to be imprisoned while the mind is not unified. Creation continues unabated because that is the Will of God. This Will is always unified and therefore has no meaning in this world. It has no opposite and no degrees.
The mind can be right or wrong, depending on the voice to which it listens. Right-mindedness listens to the Holy Spirit, forgives the world, and through Christ's vision sees the real world in its place. This is the final vision, the last perception, the condition in which God takes the final step Himself. Here time and illusions end together.
Wrong-mindedness listens to the ego and makes illusions; perceiving sin and justifying anger, and seeing guilt, disease and death as real. Both this world and the real world are illusions because right-mindedness merely overlooks, or forgives, what never happened. Therefore it is not the One-mindedness of the Christ Mind, Whose Will is One with God's.
In this world the only remaining freedom is the freedom of choice; always between two choices or two voices. Will is not involved in perception at any level, and has nothing to do with choice. Consciousness is the receptive mechanism, receiving messages from above or below; from the Holy Spirit or the ego. Consciousness has levels and awareness can shift quite dramatically, but it cannot transcend the perceptual realm. At its highest it becomes aware of the real world, and can be trained to do so increasingly. Yet the very fact that it has levels and can be trained demonstrates that it cannot reach knowledge.