2563 The heart is the dwelling-place where I am, where I live; according to the Semitic or Biblical expression, the heart is the place "to which I withdraw." The heart is our hidden center, beyond the grasp of our reason and of others; only the Spirit of God can fathom the human heart and know it fully. The heart is the place of decision, deeper than our psychic drives. It is the place of truth, where we choose life or death. It is the place of encounter, because as image of God we live in relation: it is the place of covenant.
CCC on body, soul, spirit
365 The unity of soul and body is so profound that one has to consider the soul to be the "form" of the body:234 i.e., it is because of its spiritual soul that the body made of matter becomes a living, human body; spirit and matter, in man, are not two natures united, but rather their union forms a single nature.
366 The Church teaches that every spiritual soul is created immediately by God - it is not "produced" by the parents - and also that it is immortal: it does not perish when it separates from the body at death, and it will be reunited with the body at the final Resurrection.235
367 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.236 The Church teaches that this distinction does not introduce a duality into the soul.237 "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.238
368 The spiritual tradition of the Church also emphasizes the heart, in the biblical sense of the depths of one's being, where the person decides for or against God.239