From Kenneth Wapnick’s condensed glossary index:
miracle: not to be confused with traditional definition as change in external phenomena. as understood by ACIM, it is the change of mind that shifts our perception from the ego’s world of sin, guilt, and fear to the Holy Spirit’s world of forgiveness; reverses projection by restoring to the mind its causative function, allowing us to choose again, transcends the laws of this world to reflect the laws of God; accomplished by our joining with the Holy Spirit or Jesus, being the means of healing our own and other’s minds.
ego: the belief in the reality of the separated or false self, made as substitute for the Self Which God created; the thought of separation that gives rise to sin, guilt, fear, and a thought system based on specialness to protect itself; the part of the mind that believes it is separate from the Mind of Christ; this split mind has two parts: wrong- and right-mindedness; almost always used to denote ” wrong-mindedness,” but can include the part of the split mind that can learn to choose right-mindedness. (Note — not to be equated with the ” ego” of psychoanalysis, but can be roughly equated with the entire psyche, of which the psychoanalytic ” ego” is a part.)
Self: our true Identity as Son of God; synonymous with Christ, the Second Person of the Trinity, and contrasted with the ego self we made as a substitute for God’s creation; used rarely to refer to the Self of God.
Trinity: the unity of Its Levels is not understandable in this world; consists of 1) God, the Father and Creator, 2) His Son, Christ, our true Self, Which includes our creations, and 3) the Holy Spirit, the Voice for God.
God: the First Person in the Trinity; the Creator, the Source of all being or life; the Father, Whose Fatherhood is established by the existence of His Son, Christ; the First Cause, Whose Son is His Effect; God’s essence is spirit, which is shared with all creation, whose unity is the state of Heaven.
Christ: the Second Person of the Trinity; the one Son of God or totality of the Sonship; the Self that God created by extension of His spirit; though Christ creates as does His Father, He is not the Father since God created Christ, but Christ did not create God. (Note — not to be equated exclusively with Jesus.)
Holy Spirit: the Third Person of the Trinity Who is metaphorically described in the Course as God’s Answer to the separation; the Communication Link between God and His separated Sons, bridging the gap between the Mind of Christ and our split mind; the memory of God and His Son we took with us into our dream; the One Who sees our illusions (perception), leading us through them to the truth (knowledge); the Voice for God Who speaks for Him and for our real Self, reminding us of the Identity we forgot; also referred to as Bridge, Comforter, Guide, Mediator, Teacher, and Translator.
Heaven: the non-dualistic world of knowledge, wherein dwell God and His creation in the perfect unity of His Will and spirit; though exclusive of the world of perception, Heaven can be reflected here in the holy relationship and the real world.
holy relationship: the Holy Spirit’s means to undo the unholy or special relationship by shifting the goal of guilt to the goal of forgiveness or truth; the process of forgiveness by which one who had perceived another as separate joins with him in his mind through Christ’s vision.
knowledge: Heaven, or the pre-separation world of God and His unified creation in which there are no differences or forms, and thus it is exclusive of the world of perception; not to be confused with the common use of ” knowledge,” which implies the dualism of a subject who knows and an object which is known; in the Course it reflects the pure experience of non-duality, with no subject-object dichotomy.
projection: the fundamental law of mind: projection makes perception — what we see inwardly determines what we see outside our minds. w-m: reinforces guilt by displacing it onto someone else, attacking it there and denying its presence in ourselves; an attempt to shift responsibility for separation from ourselves to others. r-m: the principle of extension, undoing guilt by allowing the forgiveness of the Holy Spirit to be extended (projected) through us.
reason: right-mindedness; thinking in accordance with the Holy Spirit, choosing to follow His guidance and learn His lessons of forgiveness, seeing sinlessness rather than sin, and choosing vision instead of judgment. (Note — not to be confused with rationalism.)
right-mindedness: the part of our separated minds that contains the Holy Spirit — the Voice of forgiveness and reason; we are repeatedly asked to choose it instead of wrong-mindedness, to follow the Holy Spirit’s guidance rather than the ego’s, and thus return to the One-mindedness of Christ.
salvation: the atonement or the undoing of the separation; we are “saved” from our belief in the reality of sin and guilt through the change of mind that forgiveness and miracle bring about.
separation: the belief in sin that affirms an identity separate from our Creator; seemed to happen once, and the thought system which arose from that idea is represented by the ego; results in a world of perception and form, of pain, suffering, and death, real in time, but unknown in eternity.
sin: the belief in the reality of our separation from God, seen by the ego as an act incapable of correction because it represents our attack on our Creator, Who would therefore never forgive us; leads to guilt, which demands punishment; equivalent to separation, and the central concept in the ego’s thought system, from which all others logically follow; to the Holy Spirit, an error in our thinking to be corrected and therefore forgiven and healed.
spirit: the nature of our true reality which, being of God, is changeless and eternal; contrasted with the body, the embodiment of the ego, which changes and dies; the Thought in God’s Mind which is the unified Christ.