The answer to this question is "one". One wholly perfect teacher, whose learning is complete, suffices. This One, sanctified and redeemed, becomes the Self Who is the Son of God. He Who was always wholly spirit now no longer sees Himself as a body, or even as in a body. Therefore He is limitless. And being limitless, His Thoughts are joined with God's forever and ever. His perception of Himself is based upon God's Judgment, not His Own. Thus does He share God's Will, and bring His Thoughts to still deluded minds. He is forever One, because He is as God created Him. He has accepted Christ and He is saved.
Thus does the son of man become the Son of God. It is not really a change; it is a change of mind. Nothing external alters, but everything internal now reflects only the Love of God. God can no longer be feared, for the mind sees no cause for punishment. God's teachers appear to be many, for that is the world's need. Yet being joined in one purpose, and one they share with God, how could they be separate from each other? What does it matter if they then appear in many forms? Their minds are one; their joining is complete. And God works through them now as One, for that is what they are.
Why is the illusion of many necessary? Only because reality is not understandable to the deluded. Only a very few can hear God's Voice at all, and even they cannot communicate His messages directly through the Spirit Which gave them. They need a medium through which communication becomes possible to those who do not realize that they are Spirit. A body they can see. A voice they understand and listen to without the fear that truth would find in them. Do not forget that truth can come only where it is welcomed without fear. So do God's teachers need a body, for their Unity could not be recognized directly.
Yet what makes them God's teachers is their recognition of the proper purpose of the body. As they advance in their profession, they become more and more certain that the body's function is but to let God's Voice speak through it to human ears. And these ears will carry to the mind of the hearer messages which are not of this world, and the mind will understand because of their Source. From this understanding will come the recognition, in this new teacher of God, of what the body's purpose really is; the only use there really is for it. This lesson is enough to let the Thought of Unity come in, and what is One is recognized as One. The teachers of God appear to share the illusion of separation, but because of what they use the body for, they do not believe in the illusion despite appearances.
The central lesson is always this; that what you use the body for, it will become to you. Use it for sin or for attack, which is the same as sin, and you will see it as sinful. Because it is sinful it is weak, and being weak it suffers and it dies. Use it to bring the Word of God to those who have It not, and the body becomes holy. Because it is holy it cannot be sick, nor can it die. When its usefulness is done it is laid by, and that is all. The mind makes this decision, as it makes all decisions which are responsible for the body's condition. Yet the teacher of God does not make this decision alone. To do that would be to give the body another purpose from the one that keeps it holy. God's Voice will tell him when he has fulfilled his role, just as It tells him what his function is. He does not suffer either in going or remaining. Sickness is now impossible to him.
Oneness and sickness cannot co-exist. God's teachers choose to look on dreams a while. It is a conscious choice. For they have learned that all choices are made consciously, with full awareness of their consequences. The dream says otherwise, but who would put his faith in dreams, once they are recognized for what they are? Awareness of dreaming is the real function of God's teachers. They watch the dream figures come and go, shift and change, suffer and die. Yet they are not deceived by what they see. They recognize that to behold a dream figure as sick and separate is no more real than to regard it as healthy and beautiful. Unity alone is not a thing of dreams. And it is this God's teachers acknowledge as behind the dream, beyond all seeing and yet surely theirs.