Why can we grasp Jesus only as a "mystery"?
Jesus extends into God; therefore we cannot understand him if we exclude the invisible divine reality.
The visible side of Jesus points to the invisible. We see in the life of Jesus numerous realities that are powerfully present but that we can understand only as a mystery. Examples of such mysteries are the divine Sonship, the Incarnation, the Passion, and the Resurrection of Christ.
Did Jesus have a soul, a mind, and a body just as we do?
Yes. Jesus "worked with human hands, he thought with a human mind. He acted with a human will, and with a human heart he loved" (Second Vatican Council, GS 22, 2).
The humanity of Jesus is complete and includes also the fact that Jesus possessed a soul and developed psychologically and spiritually. In this soul dwelled his human identity and his special self-consciousness. Jesus knew about his unity with his heavenly Father in the Holy Spirit, by whom he allowed himself to be guided in every situation of his life. (YOUCAT questions 78-79)
Dig Deeper: CCC section (470-484) and other references here.
Part 1: The Profession of Faith (26 - 1065)
Section 2: The Profession of the Christian Faith (185 - 1065)
Chapter 2: I Believe in Jesus Christ, the Only Son of God (422 - 682)
Article 3: "He was conceived by the power of the Holy Spirit, and was born of the Virgin Mary" (456 - 570)
Paragraph 1: The Son of God Became Man (456 - 483)
IV. HOW IS THE SON OF GOD MAN? ⇡
Because "human nature was assumed, not absorbed",97 in the mysterious union of the Incarnation, the Church was led over the course of centuries to confess the full reality of Christ's human soul, with its operations of intellect and will, and of his human body. In parallel fashion, she had to recall on each occasion that Christ's human nature belongs, as his own, to the divine person of the Son of God, who assumed it. Everything that Christ is and does in this nature derives from "one of the Trinity". The Son of God therefore communicates to his humanity his own personal mode of existence in the Trinity. In his soul as in his body, Christ thus expresses humanly the divine ways of the Trinity:98 The Son of God... worked with human hands; he thought with a human mind. He acted with a human will, and with a human heart he loved. Born of the Virgin Mary, he has truly been made one of us, like to us in all things except sin.99
97.
GS 22 § 2.
98.
Cf. Jn 14:9-10.
99.
GS 22 § 2.
Christ's soul and his human knowledge ⇡
Apollinarius of Laodicaea asserted that in Christ the divine Word had replaced the soul or spirit. Against this error the Church confessed that the eternal Son also assumed a rational, human soul.100
100.
Cf. Damasus 1: DS 149.
This human soul that the Son of God assumed is endowed with a true human knowledge. As such, this knowledge could not in itself be unlimited: it was exercised in the historical conditions of his existence in space and time. This is why the Son of God could, when he became man, "increase in wisdom and in stature, and in favor with God and man",101 and would even have to inquire for himself about what one in the human condition can learn only from experience.102 This corresponded to the reality of his voluntary emptying of himself, taking "the form of a slave".103
101.
102.
Cf. Mk 6:38; 8:27; Jn 11:34; etc.
103.
But at the same time, this truly human knowledge of God's Son expressed the divine life of his person.104 "The human nature of God's Son, not by itself but by its union with the Word, knew and showed forth in itself everything that pertains to God."105 Such is first of all the case with the intimate and immediate knowledge that the Son of God made man has of his Father.106 The Son in his human knowledge also showed the divine penetration he had into the secret thoughts of human hearts.107
104.
Cf. St. Gregory the Great, "Sicut aqua" ad Eulogium, Epist. Lib. 10, 39 PL 77, 1097A ff.; DS 475.
105.
St. Maximus the Confessor, Qu. et dub. 66: PG 90, 840A.
106.
Cf. Mk 14:36; Mt 11:27; Jn 1:18; 8:55; etc.
107.
Cf. Mk 2:8; Jn 2:25; 6:61; etc.
By its union to the divine wisdom in the person of the Word incarnate, Christ enjoyed in his human knowledge the fullness of understanding of the eternal plans he had come to reveal.108 What he admitted to not knowing in this area, he elsewhere declared himself not sent to reveal.109
108.
Cf. Mk 8:31; 9:31; 10:33-34; 14:18-20, 26-30.
109.
Christ's human will ⇡
Similarly, at the sixth ecumenical council, Constantinople III in 681, the Church confessed that Christ possesses two wills and two natural operations, divine and human. They are not opposed to each other, but cooperate in such a way that the Word made flesh willed humanly in obedience to his Father all that he had decided divinely with the Father and the Holy Spirit for our salvation.110 Christ's human will "does not resist or oppose but rather submits to his divine and almighty will."111
110.
Cf. Council of Constantinople III (681): DS 556-559.
111.
Council of Constantinople III: DS 556.
Christ's true body ⇡
Since the Word became flesh in assuming a true humanity, Christ's body was finite.112 Therefore the human face of Jesus can be portrayed; at the seventh ecumenical council (Nicaea II in 787) the Church recognized its representation in holy images to be legitimate.113
112.
Cf. Council of the Lateran (649): DS 504.
113.
Cf. Gal 3:1; cf. Council of Nicaea II (787): DS 600-603.
At the same time the Church has always acknowledged that in the body of Jesus "we see our God made visible and so are caught up in love of the God we cannot see."114 The individual characteristics of Christ's body express the divine person of God's Son. He has made the features of his human body his own, to the point that they can be venerated when portrayed in a holy image, for the believer "who venerates the icon is venerating in it the person of the one depicted".115
114.
Roman Missal, Preface of Christmas I.
115.
Council of Nicaea II: DS 601.
The heart of the Incarnate Word ⇡
Jesus knew and loved us each and all during his life, his agony and his Passion, and gave himself up for each one of us: "The Son of God... loved me and gave himself for me."116 He has loved us all with a human heart. For this reason, the Sacred Heart of Jesus, pierced by our sins and for our salvation,117 "is quite rightly considered the chief sign and symbol of that... love with which the divine Redeemer continually loves the eternal Father and all human beings" without exception.118
116.
117.
Cf. Jn 19:34.
118.
Pius XII, encyclical, Haurietis aquas (1956): DS 3924; cf. DS 3812.
IN BRIEF ⇡
At the time appointed by God, the only Son of the Father, the eternal Word, that is, the Word and substantial Image of the Father, became incarnate; without losing his divine nature he has assumed human nature.
Jesus Christ is true God and true man, in the unity of his divine person; for this reason he is the one and only mediator between God and men.
Jesus Christ possesses two natures, one divine and the other human, not confused, but united in the one person of God's Son.
Christ, being true God and true man, has a human intellect and will, perfectly attuned and subject to his divine intellect and divine will, which he has in common with the Father and the Holy Spirit.
The Incarnation is therefore the mystery of the wonderful union of the divine and human natures in the one person of the Word.
Paragraph 2: "Conceived by the power of the Holy Spirit and born of the Virgin Mary" (484 - 511)
I. CONCEIVED BY THE POWER OF THE HOLY SPIRIT... ⇡
The Annunciation to Mary inaugurates "the fullness of time",119 the time of the fulfillment of God's promises and preparations. Mary was invited to conceive him in whom the "whole fullness of deity" would dwell "bodily".120 The divine response to her question, "How can this be, since I know not man?", was given by the power of the Spirit: "The Holy Spirit will come upon you."121
119.
120.
121.
Lk 1:34-35 (Gk.).