• The rational soul, which is one with the sensitive and vegetative principle, is the form of the body. This was defined as of faith by the Council of Vienne of 1311;
• the soul is a substance, but an incomplete substance, i.e. it has a natural aptitude and exigency for existence in the body, in conjunction with which it makes up the substantial unity of human nature ;
• Though connaturally related to the body, it is itself absolutely simple, i.e. of an unextended and spiritual nature. It is not wholly immersed in matter, its higher operations being intrinsically independent of the organism;
• the rational soul is produced by special creation …
CATHOLIC ENCYCLOPEDIA: SoulSometimes 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. (Cf. 1 Th 5:23) The Church teaches that this distinction does not introduce a duality into the soul. (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.) (CCC 367)
Catechism of the Catholic Church - IntraText When Paul uses body, soul and spirit as in 1 Thessalonians 5:23 he is referring to the matter that man is and the soul that animates man. ‘Soul and Spirit’ is referring to the entire or whole of man; like the idiom, ‘part and parcel’ which refers to the unequivocal essential part.