CARM asks that very question (Is the Jehovah's Witnesses religion Christian?) and conveniently supplies the reader with the answer. Here is a quote taken from the CARM website:
"The answer to the question is, 'No. It is not Christian.' Like all non-Christian cults, the Jehovah's Witness organization distorts the essential doctrines of Christianity."
What "essential doctrines of Christianity" have Jehovah's Witnesses distorted? The next sentence enumerates three: "It denies the deity of Christ, His physical resurrection, and salvation by grace. This alone makes it non-Christian."
So, according to CARM's criteria for determining what constitutes true Christianity, Jehovah's Witnesses' teachings are not Christian because we deny the deity of Christ; the nature of Christ's resurrection and "salvation by grace."
Briefly, let us examine each point.
Accusing Jehovah's Witnesses of denying the deity of Christ is akin to saying that Jehovah's Witnesses deny that Jesus was an alien being from Mars, which is, of course, true: We deny that Jesus was a Martian. But we do not deny that Jesus is the Son of God. The reason we are accused of denying the so-called "deity of Christ" is because Jesus never personally claimed to be God; so why should anyone else make that claim? It is simply not a Bible doctrine. It is a human doctrine.
Consider, too, that in the four gospel accounts Christ never once said that he was God—not so much as once! He certainly had many opportunities to do so, and no doubt he would have plainly stated that he was God if it were true. Jesus wanted people to know the truth about himself and his unique relationship with God. That is why he frequently declared that he was the Son of God—and a worshipper of Jehovah God.
Thinking persons would do well to consider why it is, then, that Trinitarians have made Jesus' supposed godship one of the "essential doctrines of Christianity."
Of course, in the minds of those who are steeped in Trinitarian dogma, the father and son and holy ghost are all the same person, only different persons. As nonsensical as that is, that is exactly how the Trinity is "explained." Here is how CARM explains it:
"The Father is not the same person as the Son who is not the same person as the Holy Spirit who is not the same person as the Father. Each is divine, yet there are not three gods, but one God. There are three persons individual subsistences, or persons."
Although ardent believers insist that each person of the Trinity is his own individual, still, there is only one god, not three gods in one. How can three separate persons be the same entity? No one knows. Like all Trinitarians, CARM also admits that the Trinity is an unknowable "mystery." (An incomprehensible mythology would be more accurate.)
The fact that Jesus repeatedly declared himself to be God's son means nothing to a person who has been mentally conditioned to believe that Jesus is God. The doctrine of the Trinity is like a house of mirrors. Nothing is as it seems. For instance, Trinitarian believers apparently believe that fathers beget themselves as sons and sons beget their own fathers, too. Except in the mythological world of the Trinity, the Father did not beget the son at all. The son has always existed just as his father has always existed. Apparently, though, for some strange reason the Trinitarian god likes to pretend that there is some sort of father-son relationship between his multiple personalities. Just why the godhead explains his existence in terms of his being a father and son to himself is anyone's guess. No wonder Trinity believers declare their own mystification over the Trinity doctrine.
In reality the Bible says absolutely nothing about some mysterious triplets making up a single god. Certainly the apostles and first century Christians made no mention whatsoever of any sort of divine trio comprising a single godhead. The truth is that neither the word trinity nor the concept of three persons rolled into one God is found in the Bible. Yet, somehow, it is considered one of the essential doctrines by Trinitarians.
But what about the verses that Trinitarians use to convince themselves that Jesus is God? Here is a link to a website that discusses common questions. Here is a link to the Watchtower Society's brochure on the Trinity.
But if it is not biblical, just where did the mystery trinity concept come from anyway?
The worship of three divine personages predates Christianity by thousands of years. Evidently the Babylonians first conceived of a triad of gods. Later the Egyptians worshipped the triad of Osiris, Isis and Horus. During the time of Christ, the Romans idolized Jupiter, Juno, and Minerva. (See The Two Babylons—originally published in 1853)
How then did a pagan form of worship become the central teaching of Christendom? It is well known that after the apostles died off, Christianity became increasingly corrupt. As a result of an apostasy from Jehovah and under the influence of the demons, Jesus was gradually elevated from being the Son of God to God the son.
Finally, in 325, the Roman Emperor Constantine hosted a conference of bishops in Nicaea, France, where it was decided that Jesus was God. Amazingly, over the course of a few hundred years the Roman emperors went from feeding Christians to the lions to playing a major role in determining Christian doctrine! Although it would take several more centuries for the truth to be entirely snuffed out, eventually the trinity was institutionalized as the central teaching of Christendom. For a more in-depth article on the origins of the Trinity click here.
What about the resurrection of Jesus?
According to CARM, Jehovah's Witnesses are not Christians because we deny that Christ was physically resurrected. That is a misleading statement. It might give uninformed persons the impression that Jehovah's Witnesses believe that Jesus was only symbolically resurrected, or something of that nature. Apparently, CARM intends to give the impression that Jehovah's Witnesses deny Christ's resurrection. Nothing could be farther from the truth. Jehovah's Witnesses most certainly believe and teach that Jesus was put to death and on the third day Jehovah resurrected him. (Watchtower article)
What does the Bible say about the resurrection of Jesus? It plainly says that Jesus was a spirit (as the Logos or Word) before he came to the earth, and upon his death and resurrection he returned to heaven—as a spirit. For a brief period of 40 days following his resurrection Jesus materialized as a human—often unrecognizable by his disciples—in order to convince them that he had indeed been raised from the dead. And it is true that Jesus visibly ascended into the clouds with 500 earthly observers as witnesses of his ascension. How else could his skeptical disciples be convinced that Jesus ascended back to heaven unless they saw it with their own eyes?
Unfortunately, the same people that insist that God is a mysterious amalgam of three persons rolled into one also believe that Jesus was raised up as a glorified man and not a spirit. This is in spite of the fact that in the 4th chapter of John Jesus very simply stated "God is a spirit." The suggestion that Jesus was resurrected in the flesh is all the more absurd in view of CARM's hackneyed explanation of the Trinity:
"God is a trinity of persons consisting of one substance and one essence. God is numerically one. Yet, within the single divine essence are three individual subsistences that we call persons."
Since Trinitarians claim that Jesus is God, we would have to conclude that God is part flesh and part spirit. Of course, CARM does not offer any explanation as to how three persons making up a triune god can share the same "essence" and "subsistence" when one is a spirit and the other is supposedly glorified flesh. No matter—sheer belief apparently is all that is necessary. In spite of such torturous teachings, CARM claims that Jehovah's Witnesses are distorting essential Christian doctrines. If it were not such a serious matter it would be laughable.
Apparently some of the 1st century Christians had similar unreasonable ideas concerning the resurrection. Thankfully the apostle Paul was not nearly so confused about the nature of the heavenly resurrection. That is why in his letter to the Corinthians Paul said: "Nevertheless, someone will say: 'How are the dead to be raised up? Yes, with what sort of body are they coming?' You unreasonable person! What you sow is not made alive unless first it dies; and as for what you sow, you sow, not the body that will develop, but a bare grain, it may be, of wheat or any one of the rest; but God gives it a body just as it has pleased him, and to each of the seeds its own body."
Paul beautifully illustrates the change in nature that takes place in the case of the heavenly resurrection. By comparing the germination and transformation of a seed into a plant that bears no obvious similarity to the parent seed, we are helped to grasp the fact that in order for a human to be transformed into a spirit, the physical person must first die—just as the seed in effect dies; since no distinguishing feature of the seed is observable in the plant it produces. In the same manner, humans must first die in order to be transformed into spirits. There are no flesh-and-blood creatures in the spirit realm—only spirits.
Indeed, the foremost authority, Jesus himself, stated in the 3rd chapter of John that 'flesh is flesh and spirit is spirit,' which is to say that humans are flesh and God and the angels, are spirits. They are different in nature. That is why Jesus went on to say that in order to enter the kingdom a person had to be born again—because as Paul also indicated in the 15th chapter of I Corinthians, quoted above, flesh cannot inherit the kingdom. Being born again is the process by which a flesh and blood, physical, human is begotten as a spirit son of God in order that they may eventually leave behind their physical bodies and be transformed into the glory of Christ—who is himself the exact representation of Jehovah's glory.
What about salvation by grace?
Do Jehovah's Witnesses deny that? Absolutely not! The Watchtower has always taught that salvation is a result of Jehovah's undeserved kindness.