Since the word "doctrine" means teaching, I always thought that the doctrine of Christ is the whole Bible. I've recently been told that the doctrine of Christ is to love God and love your neighbor. I admit this is very hard to do and am familiar with the verse that tells us these are the greatest commandments. However, I constantly hear that Jesus is the issue and doctrine is not important. How can one love Jesus and not be at all interested in His teachings. My Bible says that Jesus hates the false doctrine of the Nicolaitans. How, then, can one know false doctrine if one is not interested in knowing the doctrine of Christ. (The Bible).

You bring up an excellent question about the "doctrine of Christ." In fact, you got me to studying a bit. The phrase is found only two times in the Bible. It might do us good to look at these verses:

• Hebrews 6:1Therefore leaving the principles of the doctrine of Christ, let us go on unto perfection; not laying again the foundation of repentance from dead works, and of faith toward God,
  See All... - Therefore leaving the principles of the doctrine of Christ, let us go on unto perfection; not laying again the foundation of repentance from dead works, and of faith toward God,
• 2 John 1:9Whosoever transgresseth, and abideth not in the doctrine of Christ, hath not God. He that abideth in the doctrine of Christ, he hath both the Father and the Son.
  See All... - Whosoever transgresseth, and abideth not in the doctrine of Christ, hath not God. He that abideth in the doctrine of Christ, he hath both the Father and the Son.

In both cases, the context indicates that the phrase refers to the teaching of the Bible concerning the person and work of Christ. In other words, the doctrine of Christ is the Bible teaching (or doctrine) about Jesus Christ. Let me explain each passage.

Hebrews 6:1Therefore leaving the principles of the doctrine of Christ, let us go on unto perfection; not laying again the foundation of repentance from dead works, and of faith toward God,
See All... obviously signals a change in the direction of the book of Hebrews. Up to now, the book has been dealing with the principles of the doctrine of Christ. Now it is time to go on unto perfection. Also, there is no need to lay down again other basic doctrines like repentance and faith. The question then presents itself--what have the first five chapters of Hebrews been dealing with? If we study these chapters, we will find much teaching about Jesus Christ.

1. He is the Father's spokesman for the last days (Hebrews 1:1-2 [1] God, who at sundry times and in divers manners spake in time past unto the fathers by the prophets, [2] Hath in these last days spoken unto us by his Son, whom he hath appointed heir of all things, by whom also he made the worlds;
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2. He is the "brightness of his glory, and the express image of his person" (Hebrews 1:3Who being the brightness of his glory, and the express image of his person, and upholding all things by the word of his power, when he had by himself purged our sins, sat down on the right hand of the Majesty on high:
   See All...); certainly, He must be God
3. He is better than the angels (Hebrews 1:4Being made so much better than the angels, as he hath by inheritance obtained a more excellent name than they.
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4. He is given the throne and sceptre of the kingdom (Hebrews 1:9Thou hast loved righteousness, and hated iniquity; therefore God, even thy God, hath anointed thee with the oil of gladness above thy fellows.
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5. By the grace of God He tasted death for every man (Hebrews 2:9But we see Jesus, who was made a little lower than the angels for the suffering of death, crowned with glory and honour; that he by the grace of God should taste death for every man.
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6. He took on the seed of Abraham (Hebrews 2:16For verily he took not on him the nature of angels; but he took on him the seed of Abraham.
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7. He was made a high priest to make reconciliation for the sins of the people (Hebrews 2:17Wherefore in all things it behoved him to be made like unto his brethren, that he might be a merciful and faithful high priest in things pertaining to God, to make reconciliation for the sins of the people.
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8. He is the Apostle and High Priest of our profession (Hebrews 3:1Wherefore, holy brethren, partakers of the heavenly calling, consider the Apostle and High Priest of our profession, Christ Jesus;
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9. He is a Son over His own house (Hebrews 3:6But Christ as a son over his own house; whose house are we, if we hold fast the confidence and the rejoicing of the hope firm unto the end.
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10. He was tempted in all points like us yet without sin (Hebrews 4:15For we have not an high priest which cannot be touched with the feeling of our infirmities; but was in all points tempted like as we are, yet without sin.
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11. He was glorified by the Father to be made our high priest (Hebrews 5:5So also Christ glorified not himself to be made an high priest; but he that said unto him, Thou art my Son, to day have I begotten thee.
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12. He because the author of eternal salvation (Hebrews 5:8-9 [8] Though he were a Son, yet learned he obedience by the things which he suffered; [9] And being made perfect, he became the author of eternal salvation unto all them that obey him;
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I have only picked out several things in this section of the Bible. However, these chapters certainly deal much with the doctrine of Jesus Christ-- is person and work. The remainder of Hebrews continues to speak of Christ, but more and more it points to the perfection of the believers.

The other scriptural use of the "doctrine of Christ" is in 2 John 1:9Whosoever transgresseth, and abideth not in the doctrine of Christ, hath not God. He that abideth in the doctrine of Christ, he hath both the Father and the Son.
See All... where those who abide not in the doctrine of Christ are not of God. If this refers to loving God and loving your neighbor, then we have a works salvation. But the context shows otherwise. Consider the verse in greater context:

2 John 1:7For many deceivers are entered into the world, who confess not that Jesus Christ is come in the flesh. This is a deceiver and an antichrist.
See All... For many deceivers are entered into the world, who confess not that Jesus Christ is come in the flesh. This is a deceiver and an antichrist. 8 Look to yourselves, that we lose not those things which we have wrought, but that we receive a full reward. 9 Whosoever transgresseth, and abideth not in the doctrine of Christ, hath not God. He that abideth in the doctrine of Christ, he hath both the Father and the Son.

John is dealing with deceivers who have denied the true physical presence of Christ on earth. Historically, we know that there were people who denied that Jesus Christ was born in the flesh or possessed a real body. They felt this was too demeaning to God. How could God dwell in the human body? In order to solve this problem, they created a doctrine that taught that Jesus Christ made a spiritual appearance, but was not in a real body. They denied the incarnation, the virgin birth, and other cardinal doctrines about Jesus Christ.

John taught that those who denied the physical presence of Jesus Christ on earth did not know God as Saviour. That is, the doctrine of Christ could be so perverted that they no longer believed in the true Jesus. In 2 Corinthians 11:4For if he that cometh preacheth another Jesus, whom we have not preached, or if ye receive another spirit, which ye have not received, or another gospel, which ye have not accepted, ye might well bear with him.
See All..., Paul warned of those who preached "another Jesus." I believe we see this today in many of the cults and isms. They have altered the person of Jesus Christ to such an extent that they no longer preach God's way of salvation. They have denied the doctrine of Christ.

The two verses that teach about the doctrine of Christ give two great truths about this doctrine. First, it is essential for salvation (2 John 1:9Whosoever transgresseth, and abideth not in the doctrine of Christ, hath not God. He that abideth in the doctrine of Christ, he hath both the Father and the Son.
See All...). Second, it is basic to our understanding of other doctrine in scripture. Certainly, we should take the doctrine of Christ as a very serious matter.