In the 19th century, German theologian Gottfried Thomasius (1802 A.D. - 1875 A.D.) introduced a brand new heresy called "Kenoticism". Kenoticism, based on a misunderstanding of the more Biblical Kenosis, teaches that Christ's divinity was somehow diminished when He took on human flesh.
The primary argument for Kenoticism comes from Philippians 2:5-7, which reads "Let this mind be in you which was also in Christ Jesus, who, being in the form of God, did not consider it robbery to be equal with God, but made Himself of no reputation, taking the form of a bondservant, and coming in the likeness of men." Verse 7 is of particular importance to this discussion.
Verse 7 is rendered differently in various translations. As above, the NKJV says Christ "made Himself of no reputation", whereas other translations say He "emptied Himself". This all goes back to the key phrase "ekenōsen" (ἐκένωσεν), from which the words "Kenosis" and "Kenoticism" are derived.
Thomasius, and other defenders of the Kenotic heresy, argue that it means Christ's human nature lessened His divinity, making Him somehow "less" God. This would stand in stark contrast to the long-established Hypostatic Union. That is, the Biblical doctrine that Christ, while being fully human, was also fully God.
Ultimately, while Philippians 2:7 does say Jesus "emptied Himself", it doesn't directly specify what He emptied Himself of. It certainly does not say that He emptied Himself of His divinity, "For in Christ all the fullness of the Deity lives in bodily form," (Colossians 2:9). Furthermore, as verse 6 says, He was in the form of God, and was equal with God. Thus, whatever Jesus "emptied" Himself of, it simply cannot have been His divinity.
From the context of the passage as a whole, we can determine the reality of the situation. The premise of this whole thing is "Let this mind be in you which was also in Christ Jesus..." It is this that leads up to the emptying. So, whatever Christ did here, we are to do likewise. Now, if Christ emptied Himself of His divinity, we would also be required to empty ourselves of our divinity, something which we could never do, as we are not divine.
But Christ is. And because He is divine, He has a range of advantages that simply aren't available to us. Yet, He did not use them. In fact, as verse 8 tells us, "And being found in appearance as a man, he humbled himself by becoming obedient to death— even death on a cross!"
Now, as human beings, we can't do that. We are bound by the law of death, being incapable of escaping it. But no one took Christ's life from Him, but rather, He lay it down of His own accord (John 10:18). So here we have an example of Christ having advantageous power, but not using it for His own advantage. This, Paul says, is the mind which was in Christ, and likewise should be in us. If Christ, who is equal to God, did not use that equality to His own advantage, then we, who may be rich, may be strong, may be attractive, may be intelligent, may be famous etc., should not use these gifts for selfish ends.
A great analogy of this is the TV show "The Secret Millionaire". In the show, a millionaire would temporarily leave their lives of luxury and live in an impoverished area for around a week. During this time, they would live on a small budget, with no particular advantage to help them out. They mingle with the local community, working and volunteering, and ultimately, seeking people or projects they see as worthy of receiving a cut of their fortune. After the time was up, they would reveal themselves to their chosen people and make the donation.
None of the millionaires ever actually gave up their status. The homes they left still belonged to them. They money they cut themselves off from still belonged to them. They were always still millionaires, they just didn't live like one. In the same way, at no point did Christ cease to be God, He simply didn't use this to His own advantage. Though God does not need to rest, eat, or drink, Christ took on a fully human nature. But in spite of retaining the fullness of both natures, Christ did not allow them to overlap. Just as Christ's divine nature does not make His human nature omnipresent, His human nature does not make His divine nature any less eternal.
The Council of Chalcedon (451 A.D.) summarised it best: Christ is "...to be acknowledged in two natures, inconfusedly, unchangeably, indivisibly, inseparably; the distinction of natures being by no means taken away by the union, but rather the property of each nature being preserved, and concurring in one Person and one Subsistence, not parted or divided into two persons, but one and the same Son, and only begotten, God the Word, the Lord Jesus Christ, as the prophets from the beginning have declared concerning him, and the Lord Jesus Christ himself taught us, and the Creed of the holy Fathers has handed down to us."
Clearly, therefore, the 19th century Kenotic heresy is not to be regarded as sound doctrine. In fact, in diminishing Christ's divine nature, it stands in stark contrast to the very Gospel. As Christ Himself said, "...if you do not believe that I am he, you will indeed die in your sins." (John 8:24). However, by confessing Jesus as Lord, not merely a created being, we receive salvation.