In A Course in Miracles, whenever Jesus uses the term "oneness" or "one with" or "are one", he DOES NOT MEAN that they are "one thing" like a count of 1.
The classic idea of "oneness" is this ego concept of "one thing" - what you'd be left with if you removed all egoic separations and ended up with a single unified "whole", which had no other parts. This idea of oneness is actually NOT what Jesus refers to in the course!
What I've come to learn is that instead, to be "one" with something means to be "of one kind". ie, to be in the same LIKENESS, or the SAME EXACT NATURE AS. In terms of brothers for example, this means brothers being "one" are like identical twins.
Jesus also makes statements about how you are one WITHIN YOURSELF. This has the same meaning, that within yourself there is only one consistent nature, no differences, no parts that are different from other parts, all "unified" and "united" within yourself. This is what it means to be one with YOURSELF. e.g. if you are made only of LIGHT, then all of you is LIGHT and so you are consistently "one nature".
So to Him, in His use of these terms, he is not referring to OUR idea of oneness. He has redefined its meaning as "of one kind" or "identical to" or "the same quality as" or "the same nature as" or "is still distinct but not different in appearance or form or character".
So now.. have a read of these statements below which all use this terminology, and instead of reading it to mean the typical idea of "oneness" or "one thing"... read it instead as saying, are OF ONE KIND or are identical, or that they share a likeness. It gives a whole different meaning to what He is saying, and it ALSO clarifies some of the subtler points that He is making where He distinguishes that there are TWO things in another portion of His statement and this TWONESS is not contradicted when the part mentioning "one" is recognized to mean THE SAME KIND, rather than "one thing."
This is all in recognition of the FACT that God has created many "separate beings who have everything individually" and recognizes that they are in the LIKENESS of God but still have their own distinct "self" or soul. Souls are ONE WITH GOD, meaning, they are LIKE HIM. Not that they ARE Him.
"This appears to contradict another statement: "I and my Father are one." It doesn't. There are still separate parts in the statement, in recognition of the fact that the Father is GREATER. Actually, the original statement was "are of one KIND."
"Helpers are given you in many forms, although upon the altar they are one." (are similar)
"Today s idea accurately describes you as God created you. You are one within yourself, and One with Him. Yours is the unity of all creation. Your perfect unity makes change in you impossible." (one with yourself = consistent throughout) (perfect unity means the same thing, a state of consistency and one KIND)
"Miracles are seen in light, and light and strength are one." (are the same)
"I trust my brothers who are one with me." (you still have brothers, they are IDENTICAL to you)
"What can this mean, EXCEPT your minds are one?" (you still have your own minds, but they are IDENTICAL in nature)
"To and to receive are one in truth." (are identical)
"This recognition is the recognition that his will and God's are one." (shared, mutual, in agreement)
"He does not judge BETWEEN them, KNOWING they are one. Being united, they are one BECAUSE THEY ARE THE SAME" (ie identical - being united doesn't mean one thing, it means teamwork)
"No miracle can ever be denied to those who know that they are one with God." (how could you do a miracle if you are "as God"? You still have a self, which is LIKE GOD)
"For we are one in purpose, and the end of hell is near." (one in purpose, meaning identical purpose)
"THEY are one." (identical)
"I and by father are one" (we are identical to God's nature, in his likeness)
"And I, who am among them, am one with them and with Him" (still Jesus has his own self, and "them" has their own selves, and God has his self, and we are all one ie alike)
"So he became identified with Christ, a man no longer, but at one with God." (Christ is still distinct from God, they are alike)
"If you were one with Him, and RECOGNIZED this oneness, you would know His power is YOURS." ("his" and "yours" still coexist as TWO THINGS, but are sharing a similarity)
"And He will speak to you, reminding you that you are Spirit, one with Him and God, your brothers and your Self." (See how Jesus says you still have brothers, being one with them does not UNDO the brotherhood)
"Now are we One with Him Who is our Source." (we still have our self, yet are one, ie of one nature)
"Let me remember I am one with God." (but you still have an *I*)
"And everything we see reflects the holiness within the mind at one with God and with itself." (see how here again he says that your mind is one WITH ITSELF and therefore still is a distinct thing in its own right, and its oneness with God is a reflection or similarity TO God, it does not mean "god is you")
"Aspects of reality can be seen IN EVERYTHING and EVERYWHERE. Yet only God can gather them together by crowning them AS ONE with the final gift of eternity." (as identical)
"Yet its frame is JOINED to its Creator, One with Him AND with His masterpiece." (alike)
"And yet, unless your will is one with His, His gifts are not received." (you still have your own WILL! ... but your will being one with God's means its a second will that is identical in intention to God's - elsewhere Jesus says "in accord with" or agreement with)
"It remains forever and forever like its Creator, being one with Him." (it still remains forever! Just because it's one with its creator doesn't mean it isn't a thing in its own right)
"No-one who shares his purpose with him can NOT be one with him." (identical to)
"Praise be unto you, who make the Father One with His Own Son." (Here again the father HAS A SON, but they are one, and this doesn't mean the son IS God, it means the son is LIKE GOD or of one kind)
"Your mind IS one with God's." (you still have a mind, it is LIKE God's mind)
"We thank our Father for one thing alone; that we are separate from no living thing, and therefore one with Him." (separation mean isolation ie no sharing. You still share with God, and being one with him means being in total harmony)
"This little aspect is NO DIFFERENT from the whole, being continuous with it, and at one with it." (there is still a little aspect, it is LIKE the whole)
"No pathway in the world can lead to Him, nor any worldly goal is one with His." (one with as in identical to)
"But, as you cross to JOIN it, IT will JOIN WITH YOU, and BECOME ONE with you." (identical with you)
"I am one with God." (You still have an *I* in this statement! It doesn't mean you are God.)
"No-one unites with enemies, nor is at one with them in purpose." (here Jesus uses "one" interestingly in the 'negative' to again refer to "at one" as meaning "not identical to".)
"For Christ takes many forms with different names until their oneness can be recognized." (oneness means identical selves/souls)
"The single vision, which the Holy Spirit offers you, will bring this Oneness to your mind" (notice that YOUR MIND is still a distinct thing. Oneness comes to it, and it still remains a distinct mind. It becomes LIKE God's mind and united within itself rather than against itself)
"Its oneness is forever guaranteed inviolate" (wholeness, unity, self-supporting, free of conflict)
"As we share this goal, we increase its power to attract the whole Sonship, and to bring it back into the Oneness in which it was created." (the sonship still exists with MANY SONS in it, its oneness is the IDENTICALITY of the nature of each son)
"If you were one with Him, and RECOGNIZED this oneness, you would know His power is YOURS." (there is still "him" and "you" in this)
"And ONLY as you look upon him as guiltless, can you understand his Oneness." (oneness is also holiness and innocence)
"My oneness with the Christ establishes me as Your Son, beyond the reach of time, and wholly free of every law but Yours." (being like all others)
"Your role in the redemption LEADS you to it, by re-establishing its oneness in your minds." (there are still multiple minds here, even after oneness is established... oneness means a healed state of unity and freedom from conflict and wholeness and single-minded intention and similarity to God's likeness)