Youcat commented through CCC - Question n. 62 Part II.

YOUCAT Question n. 62 Part II. - What is the soul?

(Youcat answer - repeated) The soul is what makes every individual person a man: his spiritual life-principle and inmost being. The soul causes the material body to be a living human body. Through his soul, man is a creature who can say “I” and stand before God as an irreplaceable individual.       

A deepening through CCC

(CCC 365) The unity of soul and body is so profound that one has to consider the soul to be the "form" of the body (Cf. Council of Vienne (1312): DS 902): 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. (CCC 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 (Cf. Pius XII, Humani generis: DS 3896; Paul VI, CPG § 8; Lateran Council V (1513): DS 1440).    

Reflecting and meditating 

(Youcat comment) Men are bodily and spiritual creatures. A man’s spirit is more than a function of his body and cannot be explained in terms of man’s material composition. Reason tells us that there must be a spiritual principle that is united with the body but not identical to it. We call it the “soul”. Although the soul’s existence cannot be “proved” scientifically, man cannot be understood as a spiritual or intellectual being without accepting this spiritual principle that transcends matter.    

(CCC Comment)

(CCC 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 (1 Th 5:23). The Church teaches that this distinction does not introduce a duality 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; GS 22 § 5; Humani generis: DS 3891).      

(This question: What is the soul? is continued)