There are two thought systems, and each has its own way of thinking. Each has its own logic and reason.
The ego’s system, which is also the physical world ("the world is false perception"), is based on separation. It completely rejects any kind of sharing. It’s reasoning follows a simple rule, which is at the root of consciousness:
This... is separate from that. Therefore, this is not that.
This is how the entire physicality of the world is mapped. An apple is not an orange. You are either at home or at the mall but never both at once. My body is not your body. I am not you.
Most of the world believes in the world, believes that the way that physical objects are separate is "natural and normal", and learns to think along these lines.
We then think of another as "not myself". We think of one object as separate from another object. We think if we give something we have to physically lose it. We think we are in one location and not another.
Our entire "way of thinking" adapts to the illusory world of false perception and thinks along ego lines. Separate this, separate that. Either this, or that. Not both. Nothing is shared. Everything is kept apart.
Its main thought construct is "either this or that". For example, if you put the apple in the left bucket, the apple is not in the right bucket. Either the apple is in the left bucket, or the right bucket.
This seems natural as a way of thinking because it seems to map to how the world is physically arranged. Objects seem to "prove" that this is how things are, so we think in the same way. We reason logically, based on evidence and physical experience, that "the apple can’t be in both buckets at once."
The thought system of God, is COMPLETELY opposite to this. It BREAKS all of the egos laws, both physically and in terms of reasoning. God’s system is NOT broken out based on separation. It isn’t rooted in something being "not" something else. And there are no differences to keep things apart.
When you want to wake up, to develop spiritually or to approach God, your mind has to actually learn to stop thinking like a physical object, and think like spirit. This is not easy because it’s so completely alien to how the world is set up.
For example, Jesus talks about how if you give away an idea, you keep the idea, and now both you and the other have the idea. And now the idea is strengthened. To the ego this is a violation of its laws.
The ego would say, it is not possible for one thing to be in two places at once. And that it is not possible for two people to have the same thing at the same time. It wants sacrifice. It wants lack. It wants finite limited resources. It wants exclusive ownership.
The ego can’t comprehend the idea of sharing. True sharing doesn’t mean compromise, or that each person gets half. True sharing means two individuals have everything at the same time. This is utterly nonsense to how the ego-minded thinker thinks.
The ego would say, It is utterly impossible for one thing to be two things and still be one thing. But God would say, that’s completely natural and entirely possible. God thus creates many children of God who are each other. Effectively, one son of God, an apple, is in both buckets at once. He is in his own bucket, and in the bucket of his brother. But the ego says this is impossible.
Becoming able to think in terms of sharing, or what is very often called "oneness", you have to drop notions of separation. To comprehend how you and your brother are one, and yet still brothers, you can’t think about it in terms of how the ego thinks about it.
The ego will conclude, either there is one son of God, or many sons of God, not both. To suggest both is true simultaneously seems like utter nonsense. But God’s laws break the ego’s laws. And God’s logic and laws of reason pay no attention to the limitations the ego imposes.
Thinking like and with God is nothing like thinking with the ego. The suggestion that you ARE your brother, and the two of you are joined, transcends the ego’s idea of separation. But until you "love your neighbor as yourself", your mind is not truly in a state of love, or recognizing who you are.
Part of you is in your brother. Your mind is also part of their mind. "One brother is all brothers. Every mind contains all minds, for every mind is one. Such is the truth."
This in no way means that, when the two brothers become "one", there are no longer two brothers. The twoness doesn’t go away. Ego says it has to. God says the ego makes no sense. The two are brothers precicely because they are two in number. And just because they are BOTH each other, doesn’t mean they are not also themselves. This makes TOTAL sense in terms of how GOD thinks.
When you think about anything to do with God’s Kingdom, creation, sons, sonship, christ, souls, holy spirit, creations, etc... anything pre-separation.... you CANNOT think of it with the ego’s way of thinking. Because God’s system of thought is NOT spacetime. It is not broken out into separate things that share nothing with each other. It isn’t a system of lack or difference or exclusive compartmentalization.
EVERYONE who thinks about these topics using earth-bound separation-based ego reasoning, comes to FALSE conclusions about what ACIM is saying.
We can’t even really understand how it’s possible that you are one with your brother, or how God has more than one son in reality, or how we share minds, or how joined minds are healed, etc.... if you can’t also get your head around how to think TOTALLY OUTSIDE of the ego’s box.
The Golden rule states that what is true of one is true of another. There is one truth applicable equally to everyone. This is because god’s nature is singular and is shared by everyone. This then means that if something is true of your brother it must also be true of you. But the ego will say no, it’s no possible for you and your brother to be IDENTICAL... you have to be different.
Since the Golden Rule is God’s law, ego’s thought system breaks God’s law. It is an attempt to ignore the rule of equality of truth, which results in "the truth is different for everyone" - the first law of chaos. And chaos - total disorder - arises from there. And the ego calls this disorder - nature. Physical nature. As if it is completely natural. Yet it could not be more unnatural.
So if you want to understand the higher truth that ACIM is trying to teach, the dynamics of holy relationship, the sharing of minds, how miracles work, the relationship you have as brothers, the laws of God that you are under, and all the other things which are OUTSIDE of the ego’s way of thinking... you CANNOT USE the ego’s way of thinking to think about them. If you do, you will come to false conclusions, absolutely guaranteed. Because ego thought REJECTS the fundamental basis for God’s thinking, which is that everything is shared.
Sharing vs separation, is the two thought systems. And they DO NOT think alike. And they do not reason alike. And they do not conclude alike. There are TWO WAYS of thinking. One is false, and one is true. This higher way of thinking is everything written in the course talking about anything above "false perception", ego, body, or physical states.
Everything of true perception, christ, God, Sonship, heaven, healing, miracles etc.... is NOT OF THIS WORLD. And you cannot think about it correctly by thinking in the way that this world thinks about itself. You have to learn a NEW way to think, to reason, to perform logic, and to draw conclusions. And it has to break the laws of what you have always thought makes SENSE. The world does NOT make sense because it is a system of insanity and separation. So it’s "sense" is actually nonsense. And what you think is nonsense about God, is true.