Objection 1. It would seem that Christ's humanity and Godhead are not to be adored with the same adoration. For Christ's Godhead is to be adored, as being common to Father and Son; wherefore it is written (John 5:23): "That all may honor the Son, as they honor the Father." But Christ's humanity is not common to Him and the Father. Therefore Christ's humanity and Godhead are not to be adored with the same adoration.
Objection 2. Further, honor is properly "the reward of virtue," as the Philosopher says (Ethic. iv, 3). But virtue merits its reward by action. Since, therefore, in Christ the action of the Divine Nature is distinct from that of the human nature, as stated above (Question 19, Article 1), it seems that Christ's humanity is to be adored with a different adoration from that which is given to His Godhead.
Objection 3. Further, if the soul of Christ were not united to the Word, it would have been worthy of veneration on account of the excellence of its wisdom and grace. But by being united to the Word it lost nothing of its worthiness. Therefore His human nature should receive a certain veneration proper thereto, besides the veneration which is given to His Godhead.
On the contrary, We read in the chapters of the Fifth Council [coll. viii, can. 9]: "If anyone say that Christ is adored in two natures, so as to introduce two distinct adorations, and does not adore God the Word made flesh with the one and the same adoration as His flesh, as the Church has handed down from the beginning; let such a one be anathema."
I answer that, We may consider two things in a person to whom honor is given: the person himself, and the cause of his being honored. Now properly speaking honor is given to a subsistent thing in its entirety: for we do not speak of honoring a man's hand, but the man himself. And if at any time it happen that we speak of honoring a man's hand or foot, it is not by reason of these members being honored of themselves: but by reason of the whole being honored in them. In this way a man may be honored even in something external; for instance in his vesture, his image, or his messenger.
The cause of honor is that by reason of which the person honored has a certain excellence. for honor is reverence given to something on account of its excellence, as stated in II-II, 103, 1. If therefore in one man there are several causes of honor, for instance, rank, knowledge, and virtue, the honor given to him will be one in respect of the person honored, but several in respect of the causes of honor: for it is the man that is honored, both on account of knowledge and by reason of his virtue.
Since, therefore, in Christ there is but one Person of the Divine and human natures, and one hypostasis, and one suppositum, He is given one adoration and one honor on the part of the Person adored: but on the part of the cause for which He is honored, we can say that there are several adorations, for instance that He receives one honor on account of His uncreated knowledge, and another on account of His created knowledge.
But if it be said that there are several persons or hypostases in Christ, it would follow that there would be, absolutely speaking, several adorations. And this is what is condemned in the Councils. For it is written in the chapters of Cyril [Council of Ephesus, Part I, ch. 26]: "If anyone dare to say that the man assumed should be adored besides the Divine Word, as though these were distinct persons; and does not rather honor the Emmanuel with one single adoration, inasmuch as the Word was made flesh; let him be anathema."
Reply to Objection 1. In the Trinity there are three Who are honored, but only one cause of honor. In the mystery of Incarnation it is the reverse: and therefore only one honor is given to the Trinity and only one to Christ, but in a different way.
Reply to Objection 2. Operation is not the object but the motive of honor. And therefore there being two operations in Christ proves, not two adorations, but two causes of adoration.
Reply to Objection 3. If the soul of Christ were not united to the Word of God, it would be the principal thing in that Man. Wherefore honor would be due to it principally, since man is that which is principal in him [Cf. Ethic. ix, 8]. But since Christ's soul is united to a Person of greater dignity, to that Person is honor principally due to Whom Christ's soul is united. Nor is the dignity of Christ's soul hereby diminished, but rather increased, as stated above (2, 2, ad 2).
Source: Summa Theologica (New Advent)