The answer, as best as we can derive one, rests in the Church’s understanding of the Incarnation. We firmly believe that Jesus Christ– second person of the Holy Trinity, consubstantial with the Father, truly divine– entered this world taking on human flesh through Mary, who had conceived by the power of the Holy Spirit. The gospels clearly reveal this belief: The gospel of St. Matthew attests, “When [Jesus’] mother Mary was engaged to Joseph, but before they lived together, she was found with child through the power of the Holy Spirit” (Matthew 1:18) and then quoting Prophet Isaiah, “‘The virgin shall be with child and give birth to a son, and they shall call him Emmanuel’ a name which means ‘God is with us'” (Matthew 1:23). Archangel Gabriel in the Gospel of St. Luke said to Mary, “The Holy Spirit will come upon you and the power of the Most High will overshadow you; hence, the holy offspring to be born will be called Son of God” (Luke 1:35). Lastly, emphasizing the divine union of Father and Son (the Word) from all eternity, the Gospel of St. John records, “In the beginning was the Word, and the Word was in God’s presence, and the Word was God” (John 1:1) and then presents the incarnation, “The Word became flesh and made His dwelling among us, and we have seen His glory: The glory of an only Son coming from the Father, filled with enduring love” (JN 1:14). In these few verses, we find the ineffable mystery of Jesus Christ, true God who became also true man.
Because we face a mystery of faith– a mystery in the sense that our limited human reason will never fully comprehend it– various errors, especially in the early centuries of the Church arose concerning Christ. The heresy of Docetism denied the humanity of Christ, while Arianism denied the divinity of Christ. Later heresies also arose: Nestorianism, which asserted that Christ was a divine person joined to a human person; monophysitism (“one nature”) which posited that the divine nature of Christ absorbed the human nature of Christ; monothelitism (“one will”) posited that the divine will of Christ absorbed the human will. The Church condemned these heresies in its first six ecumenical councils.
The Council of Chalcedon (451), the fourth ecumenical council, provided a very precise declaration: “Following the holy Fathers, we unanimously teach and confess one and the same Son, our Lord Jesus Christ: the same perfect in divinity and perfect in humanity, the same truly God and truly man, composed of rational soul and body; consubstantial with the Father as to His divinity and consubstantial with us as to His humanity; ‘like us in all things but sin.’ He was begotten from the Father before all ages as to His divinity and in these last days, for us and for our salvation, was born as to His humanity of the Virgin Mary, the Mother of God. We confess that one and the same Christ, Lord, and only-begotten Son, is to be acknowledged in two natures without confusion, change, division, or separation. The distinction between the natures was never abolished by their union, but rather the character proper to each of the two natures was preserved as they came together in one person and one hypostasis.”
Given this understanding, Christ– true God and true man– has a genuine human knowledge and a genuine divine knowledge. Again, we must be careful not to confuse, change, divide, or separate them. The human knowledge would have the limits imposed by our Lord living in this time and space at a particular time of history. For this reason, after Jesus is found in the temple at age twelve and returns to Nazareth, the Gospel states, “[He] progressed steadily in wisdom and age and grace before God and men” (Luke 2:52). Moreover, Jesus asks questions of the apostles, genuinely seeking an answer; for example, He asks, “How many loaves have you?” or “Who do people say that I am?” The Catechism explains, “This corresponded to the reality of His voluntary emptying of Himself, taking ‘the form of a slave” (#472).
Nevertheless, our Lord also had a divine knowledge. Jesus had an intimate and immediate knowledge of the Father, as evidenced in the Farewell Discourse of the Gospel of St. John (cf. 14:1ff). He also could read the souls of individuals: “Jesus was immediately aware of their reasoning, though they kept it to themselves and He said to them: ‘Why do you harbor these thoughts?'” (Mark 2:8). St. Maximus the Confessor (d. 662) stated in his Quaestiones et dubia, “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.”
The Catechism summarizes the point as follows: “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. What He admitted to not knowing in this area, He elsewhere declared Himself not sent to reveal” (#474).
Father Bertrand de Margerie, S.J. in his The Human Knowledge of Christ provided further clarification: “Classical Christology teaches, and the Magisterium also, that, long before Easter, Jesus enjoyed in His human intelligence a three-fold knowledge: acquired, infused, and beatific. The first kind came to Him as it does to other men, from the exercise of His senses and His reason; the second was immediately communicated to His human soul by His Divine Person; and the third gave Him immediate knowledge of His Father. This classical Christology is anxious to emphasize not only what Jesus knew as a man, but further and above all that He knew all that was necessary for the perfect carrying out of His mission as Savior and Redeemer.”
Immediately, we can still see we are left with a mystery surrounding Christ’s divine and human knowledge. Ironically, some theologians still “tip” the scale to one side or the other, usually today emphasizing the human knowledge and its limitations to the extent of de-divinizing Christ. Rather than try to dissect Christ– which we will never be able to do– we must appreciate what His knowledge means for us. Christ entered this world, true God becoming true man. In His divine knowledge, He revealed to us perfectly the ways of God, and lighted a path for us to follow to gain salvation. In His human knowledge, Christ knew fully well the human condition that each of us experiences– our joys yet sorrows, pleasures yet pains, successes yet failures. Therefore, each of us must turn to our Lord, believing in His Word, trusting in His will, and relying on His strength.