Earth is in fact an alien world, and human bodies are alien bodies. Given that our true natural state or "home world" is The Kingdom of God (Heaven), Earth represents the total opposite to what is natural and is alien to it.
That which is is "alienated" is that which is separated or exiled or unlike. That which is "alien" is that which is so unlike your nature that it seems completely against it.
Jesus also refers to "alien" in the sense of heaven's truth being "alien to" how you are on earth, because it is so different. Here's what he has to say about you trying to be an alien in an alien world...
"Grievances are completely alien to love."
"If I hold grievances I am attacking love, and therefore attacking my Self. My Self thus becomes alien to me. "
"Try to avoid the tendency toward self-directed selection, which may be particularly tempting in connection with today's idea because of its wholly alien nature. Remember that any order which you impose is equally alien to reality."
"What is your Self remains an alien to the part of you which thinks that it is real but different from yourself."
"Stranger yet, he does not recognize to whom he comes, and yet maintains his home belongs to him while he is alien now who is at home."
"For in his home his Self remains. It asked no stranger in, and took no alien thought to be Itself."
"A memory of home keeps haunting you, as if there were a place which called you to return although you do not recognize the Voice, nor what it is the Voice reminds you of. Yet still you feel an alien here, from somewhere all unknown. Nothing so definite that you could say with certainty you are an exile here. Just a persistent feeling, sometimes not more than a tiny throb, at other times hardly remembered, actively dismissed, but surely to return to mind again."
"Yet there is a Child in you Who seeks His Father's house, and knows that He is alien here."
"For He would bring you back with Him, that He Himself might stay, and not return again where He does not belong and where He lives an outcast in a world of alien thoughts."
"Go home with Him from time to time today. You are as much an alien here as He."
"Yet it is up to us when this is reached; how long we let an alien will appear to be opposing His."
""Let me not separate my function from my will."
"I would not use this for an alien purpose."
"Today's idea, completely alien to the ego and the thinking of the world, is crucial to the thought reversal which this course will bring about."
"Today we try to understand the truth that giver and receiver are the same. You will need help to make this meaningful because it is so alien to the thoughts to which you are accustomed."
"When you GIVE UP peace, you are EXCLUDING yourself FROM it. This is a condition which is so ALIEN to the Kingdom that you CANNOT understand the state which prevails WITHIN it." "In your FORGIVENESS of this stranger, alien to you and yet your ancient Friend, lie HIS release, and YOUR redemption WITH him."
"The mind can think it sleeps, but that is all. It cannot change what is its waking state. It cannot make a body, nor abide within a body. What is alien to the mind does not exist, because it has no source. "
"When the mind elects to be what it is not, and to assume an alien power which it does not have, a foreign state it cannot enter, or a false condition not within its Source, it merely seems to go to sleep a while."
"Yet your defense sets up an enemy within; an alien thought at war with you, depriving you of peace, splitting your mind into two camps which seem wholly irreconcilable. For love now has an "enemy," an opposite; and fear, the alien, now needs your defense against the threat of what you really are."
"Its alien nature, TO THE EGO, is proof you will NOT find the answer there."
"Reason is ALIEN to insanity, and those who use it have gained a means which cannot BE applied to sin."
"The constancy of joy is a condition quite alien to your understanding."
"What NEEDS interpretation MUST be alien. Nor will it EVER be made understandable, by an interpreter you cannot understand."
"This child will teach you what you do not understand, and make it plain. For his will be no alien tongue."
"If you think about it, you will see that, while this kind of thinking is totally alien to having THINGS, even to the lower mind it is quite comprehensible in connection with IDEAS."
"He is not attempting to force an alien will UPON you."
"If you did not have divided wills, you would recognize that willing is salvation because it IS communication. It is impossible to communicate in alien tongues."
"Light is not of the world, yet you who bear the light in you are alien here as well. The light came with you from your native home, and stayed with you because it is your own."
"For you HAVE hurt yourself, and made your Self your enemy. And now you MUST believe you are not you, but something alien to yourself and "something else," a "something" to be feared instead of loved."
"The Eternal Guest remains, but His Voice grows faint in alien company. "
"Come home. You have not found your happiness in foreign places, and in alien forms which have no meaning to you, though you sought to make them meaningful. This world is not where you belong. You are a stranger here."
"Without its function then, it has no peace, and happiness is alien to its thoughts."
"It is not the purpose of an alien power, thrust upon you unwillingly."
"And you WILL deny your Self, and walk upon an alien ground which your Creator did not make, and where you seem to be a "something" you are not."
"He would have no separation, like an alien will, rise between what He wills for you, and what YOU will."
"You know not what you say, and so you know not what is said to you. But your Interpreter perceives the meaning in your alien language."
"The seeds of sickness and the shame of sin He CANNOT bridge, for He cannot destroy the alien will that He created not."
"Nothing is so alien to you as the simple truth and nothing are you LESS inclined to listen to."
"He does not see the Christ in him who calls. What answer can he give to one who seems to be a stranger; alien to the truth and poor in wisdom, without the god who must be given him?"
"Herein lies the basis of all errors, for all of them are but attempts to compromise by seeing just a little bit of hell. This is a mockery so alien to God that it must be forever inconceivable. But the insane believe it because they are insane."
"Dreams of any kind are strange and alien to the truth."
"Sin has no place in Heaven, where its results are alien, and can no more enter than can their source. "
"If you will consider WHAT you have taught, and how alien it is to what you THOUGHT you knew, you will be COMPELLED to recognize that your Teacher came from BEYOND your thought-system, and so could look upon it fairly, and perceive it was untrue."
"It is hard to teach the mind a thousand alien names and thousands more. Yet you believe this is what learning means; its one essential goal by which communication is achieved and concepts can be meaningfully shared."
"God's Will does not oppose. It merely is. It is not God you have imprisoned in your plan to lose your Self. He does not know about a plan so alien to His Will."
"Let us not try longer to impose an alien will upon His single purpose."
"And no thought ALIEN to His Oneness can abide with Him there."
"The ego does not know the difference between grandeur and grandiosity, because it does not know the difference between miracle-impulses and ego-alien beliefs of its own."
"There is no thought in all the world which leads to any understanding of the laws it follows, nor the Thought which it reflects. It is as alien to the world as is your own reality."
"Perceiving something alien to itself in your MIND, the ego turns to the body, NOT the mind as its ally BECAUSE the body is not part of you."
"The world began with one strange lesson, powerful enough to render God forgotten, and His Son an alien to himself, in exile from the home where God Himself established him."
"Nothing at all has happened, but that you have put yourself to sleep, and dreamed a dream in which you were an alien to yourself, and but a part of someone ELSE's dream."
"The son of man perceives an alien will, AND WISHES IT WERE SO."
"You were at peace until you asked for special favor, and God did not give it. For the request was alien to Him, and you could not ask this of a Father who truly loved His Son."
"To value specialness is to esteem an alien will, to which illusions of yourself ARE dearer than the truth."
"By adopting the ego's viewpoint, you undertook an ego-alien journey WITH THE EGO AS GUIDE. "
"Salvation does not seek to use a means as yet too alien to your thinking to be helpful, nor to make the kinds of change you could not recognize."
"Vengeance is alien to His Mind BECAUSE He knows of justice."
"To the world, generosity means "giving away" in the sense of "giving up." To the teachers of God, it means "giving away" in order to keep. This has been emphasized throughout the text and the workbook, but it is perhaps more alien to the thinking of the world than many other ideas in our curriculum."
"Teaching devices which are totally alien to a learner's perceptual system are usually merely disruptive."
"Each Soul knows God completely. This IS the miraculous power of the Soul. The fact that each Soul has this power completely is a fact that is entirely alien to human thinking, in which if any ONE has everything, there is nothing LEFT."