The upper powers of the spiritual soul, often identified as the spirit, are: intellect (not to be confused with the biological brain); free will (i.e., Love and Charity); memory (i.e., the whole spiritual soul can never forget any knowledge it acquires), and; understanding (i.e., the ability —through the gift of grace — to penetrate and comprehend the thoughts of God). The lower powers are referred to as the soul. The lower power of the soul controls and directs the actions of our physical body. 
We must not believe that the different powers of the spiritual soul (both upper and lower powers) represent a duality. There exist no distinct and segregated locations between each of the upper and lower powers of the spiritual soul. The spirit is not in a compartment separated from the soul and vice versa. It is one spiritual soul. In #367 of the Catechism, it reads,
Sometimes the soul is distinguished from the spirit: St. Paul for instance prays that God may sanctify his people ‘wholly’, with ‘spirit and soul and body’ kept sound and blameless at the Lord’s coming [1 Thess. 5:23]. The Church teaches that this distinction does not introduce a duality [SML] into the soul [cf. Council of Constantinople IV (870): DS 657]. ‘Spirit’ signifies that from creation, man is ordered to a supernatural end and that his soul can gratuitously be raised beyond all it deserves to communion with God” [cf. Vatican Council I, Dei Filius: DS 3005; Gaudium et Spes 22 § 5; Humani Generis: DS 3891].
This unity of the one spiritual soul is vital to this topic. Durrwell writes, “It is there, in our hearts [i.e., the human spirit — SML], in the intimate depths of the believer, that the Spirit chooses his dwelling. In God himself the Holy Spirit of God reaches the ‘depths’ (cf. 1 Cor. 2:10). He is, as it were, the heart of God.” The various powers of the soul are not part of a duality. Thus, the Spirit’s dwelling in the inner heart (the spirit) would inescapably produce a profound impact on the entire spiritual/rational and physical composite human nature. The different powers exist within one single undivided spiritual soul. Whatever affects the spirit (upper powers) equally affects the soul (lower powers). Free will does not reside solely in the spiritual soul’s mythical quadrant (A). Nor does the intellect exclusively dwell in a mythical quadrant (C) of the spiritual soul, and so on.
In the rational intellect of the spirit, the Holy Spirit teaches all Truth.  Through the indwelling of the Holy Spirit, Truth is penetrated and understood. This penetration, in turn, leads to a free-will choice in the spirit to seek and become one with the beauty and goodness of that it has come to understand. The spirit seeks to Love. The spirit uses two primary components of the mouth/body — both under the control of the lower powers of the soul, to send out the overflow of the inner heart into physical creation. The human cranial brain is the portion of the body to which the intellect corresponds. The human heart of flesh is the component of the body used to express free will, i.e., charity and love. Both accurately convey the spirit but do so in the language of the body.
In the spirit, the free will chooses either to love God or – through disordered pride – to inordinately love ourselves. By willing the former, the Holy Spirit purifies our inner heart and fills it with holy desire for God. It does so through the Holy Spirit directing the soul (lower sensitive powers), which controls all the body’s functions. Thus, the body is purified so that when it sends out the overflow of the inner heart (the spirit) of man, the body will accurately express the overflow of the inner heart, doing so in the language of the body.
If the body and soul were not equally pure or conversely impure, God’s perfect justice would require that the body would merit a different place in Heaven or hell than the spiritual soul. That, of course, would be ridiculous. Why is that? Archbishop Fulton J. Sheen tells us, “There is an old Latin axiom, which sounds abstract, but which is very easily verifiable in the language of every-day: Actiones sunt suppositorum. Actions belong to the Person — not to the nature.” It is the Person who is judged — not the nature. God does not send half a person to hell and the other half to Heaven.
 Hildegard of Bingen, Scivias, 151.
 Aquinas, Summa Theologiae, I, q. 76, a. 1.
 Francois-Xavier Durrwell, Holy Spirit of God (original English translation published by Geoffrey Chapman, a division of Cassell, Ltd., 1986; reprint published by Servant Books, Cinncinati, OH, 2006), 36-37.
 cf. St. Hildegard of Bingen, Scivias (Mahwah, NJ: Paulist”Press, 1990), 35.
 cf. Rev. Edward Leen, The Holy Spirit, (New York, NY: Sheed & Ward, 1939; Sceptor Publishers, 1998, 2008), 32-33.
 Catherine of Siena, The Dialogue, 32, 103-104, 277.
 All Truth comes to man through the indwelling of the Holy Spirit in the spirit of the human spiritual soul of Jesus. This Truth is unchangeable. This is why Jesus is the cornerstone of the New Covenant of Salt Temple. He is the foundation stone that is unchangeable. See “The Cornerstone Not Built with Human Hands” Section in this email.
 Fulton J. Sheen, The Mystical Body of Christ, Ave Maria Press. Kindle Edition, pp. 24-25.