Most people understand that mankind consists of both a body and a soul. And very often the words spirit and soul are used interchangeably in this understanding of the makeup of mankind. But today I want to make you aware of a distinction between the meaning of the words soul and spirit, which can help us to understand better how we are made in the image of God.
There is within the Tradition of the Church an understanding that man is not just body, and soul; but body, soul, and spirit. This understanding stretches back at least to St. Paul as we see in the verse below.
May the God of peace himself sanctify you wholly; and may your spirit and soul and body be kept sound and blameless at the coming of our Lord Jesus Christ. (1 Thessalonians 5:23, RSV-CE)
In the various writings of the saints there are some that have separated this into three separate 'parts'–body, soul, and spirit–(although to speak in such a way is misleading because man is a unified whole and not a compilation of parts) and some who separated man into body, and soul/spirit with the spirit being a deeper or more important part of the soul. Between these two options the Church seems to favor the latter. In §366 of the Catechism it refers to the soul as the “spiritual soul.” And in §367, when referring to St. Paul's passage above, it states that the “Church teaches that this distinction does not introduce a duality into the soul.”
This third aspect of our makeup–that of the spirit–is important because it helps us to understand ourselves as made in God's image. First of all, when we include spirit with the usual body and soul understanding, then we can see man made with a tripartite nature, which is analogous to God as a Trinity of persons. And from this, according to St. Teresa of the Cross, we can see “the human soul, body, and spirit corresponding to Father, Son, and Holy Spirit respectively. (The Radiance of Being, p.209) But more importantly for us, because we are all fallen and sinful, the inclusion of spirit with body and soul can help us to understand our sinful condition. This is explained below:
…the three parts of the human being explain the threefold concupiscence. They correspond to the three archetypal sins, since Eve took the fruit in Eden because it was (1) good for food, (2) a delight to the eye, and (3) desirable for wisdom–sins enveloping respectively body, soul, and spirit–that had to be overcome at their triple root by Christ in the wilderness and by divine grace operating in the Christian life through fasting, almsgiving, and prayer (and through chastity, poverty, and obedience in the religious state.)
The Radiance of Being, p.207, Stratford Caldecott