When something is logical, you start with a premise, and then as the nature of this premise "extends", it produces logical conclusions. The conclusions that will come from this premise are really established in the premise itself. The limitations or scope of the premise determines what can come from it, and what comes from it is completely in accord with its starting point.
"Every system of thought must have a starting point. It begins with either a making or a creating, a difference we have already discussed. Their resemblance lies in their power as foundations. Their difference lies in what rests upon them. Both are cornerstones for systems of belief by which one lives."
When you use logic, and you arrive at a logical conclusion, what you're looking for is consistency, or the lack of contradiction within the logical system. If what you end up with seems to correlate to what you started with, and there was no obvious "nonsense" creeping in, then you can conclude that your logical conclusions are valid. You won't see any sign of contradiction so you'll consider the conclusion to be "correct". It will seem that the logic "makes sense".
What's happening is you're finding an internal consistency within the system, set up by the premise you started with. And each step you took in your reasoning did not violate the rules of the logic system. So whatever conclusions you ended up with seemed to make sense, based on what you started with. And this gives you a notion of things making sense, being valid, even being correct.
The problem is that the premise itself has absolutely everything to do with what you end up with. The conclusions that come from it, if you follow the logical steps carefully and impeccably, are really "automatic". If you start at a given starting point, you WILL end up at an ending point which is in harmony with the starting point. And you won't be able to come to a "false conclusion" if you reason it through carefully.
But if you start off on the wrong foot, if you begin with an assumption, of your premise is entirely wrong to begin with, what will happen? You'll still make logical steps, you'll still seek out internal consistency, you'll still look for that sense of "it all seems to fit together", and you'll still draw conclusions which seem to be in accord with the premise you started with. And you'll conclude "it makes sense" even. But the conclusions you come to, if you start off on the wrong foot, will be actually false. Even though they'll seem correct.
So you can be logical, and be wrong. If you start out wrong, you will only get something wrong at the other end. If you begin with a lie, you will end up with a lie, but it will be a logical lie which makes sense within the context of the whole system.
Thought systems work the same way, whatever the system is based on determines what can come from it, and only that can come from it and nothing else, unless you want to be contradictory. Yet if you start out with a system based on a lie, you will end up with lies. The lies will seem to make sense and even will seem "true" in that they seem to "add up" without contradicting the starting point, but they will still be false in the big picture. But if you believe them, you will be trapped and stuck, while believing you are free. And that is false perception.
This is the problem with the ego thought system. In the really big picture, the ego's system is a "small picture", and it is out of context, and it does not start with the whole truth. It is not beginning with something that is actually really true. It is starting out on the wrong foot, such as the belief that separation is true, or sin is real, or the impossible is possible, or death is life, or something real can be threatened etc.
When you start out with something ultimately false like that, you will produce an ENTIRE logical "system", where your reasoning will progress completely "logically" from the start to the end. And you will end up with conclusions which seem consistent. The conclusions will even seem to make total sense, IF the premise is true. But in the big picture, if it is recognized that the premise was false to begin with, then even though the conclusions are logically consistent, they are still false conclusions.
So the ego starts off on the wrong foot, on an assumption which is wrong. It starts with the belief that separation is possible, or sin is real, and then begins a progression of seemingly natural logical conclusions. If separation is real, then it must be true (consistent) that bodies are real. Then if bodes are real, it must be true that anything bodies experience is real. And if their experiences are real, then death is real. etc. That's a natural logical progress and completely impeccable logic. But the conclusion is insane because the whole "system of thought", the system of logic, began with a false premise.
When you start with a true premise, such as that God is infinite and permanent and immortal, there are once again logical progressions which come from this. If you follow the steps and start to draw conclusions based on that, and if you are careful to be consistent and not contradictory, you will end up with natural conclusions. And these conclusions will make sense, and seem valid, and they ALSO WILL BE TRUE. If you start with truth, you will end up with truth. And so whether or not the result is true or false, depends on whether the premise is true or false. And what you get out of the system as a natural logical conclusion or outcome, is set up in its starting point.
When the starting point is God, the natural logical outcome of God is the creation of the Kingdom. It's not that God randomly decides to create immortal beings, it's that the whole system just functions that way, truth goes in at the start, progressions of logical consistency occur, and you automatically get creation out the other end. And because you started with immortality, you end up with immortality. "God is but love, and therefore so am I." Such conclusions therefore are not only making sense, they are also TRUE.
"The Kingdom is the result of premises, just as this world is. You may have carried the ego's reasoning to its logical conclusion, which is total confusion about everything."
"The ego's logic is as impeccable as that of the Holy Spirit, because your mind has the means at its disposal to side with Heaven or earth, as it elects."
"From the belief in sin, the faith in chaos must follow. It is because it follows that it seems to be a logical conclusion; a valid step in ordered thought. The steps to chaos do follow neatly from their starting point. Each is a different form in the progression of truth's reversal, leading still deeper into terror and away from truth."
When you begin a thought process/system on a lie or illusion, you will end up with illusory lies which seem to make sense but are false. This means the total absence of REASON, which is the absence of sanity, because the whole system of thinking started out insane. When you start out the thought process/system with sanity and truth, you end up with a SANE conclusion. This is what ACIM refers to as REASON. The reasoning is LOGICAL, just as the ego's reasoning is logical, but it starts with sanity so ends with sane conclusions.
Just because something seems extremely logical, does not mean it is true. And this is a BIG problem for a lot of people studying ACIM. If for example you start out with a premise that e.g. God created the world, and you do not challenge this premise, the ENTIRE course will now be interpreted to try to "fit" it into that premise. And every conclusions drawn will not challenge that premise.
In order to uphold the premise that God created this world, a LOT of adjustments have to be made to the course's meanings, in order to produce consistency and a lack of contradiction. And this can lead to what seems like a consistent picture, but it is also completely wrong. Because it started out with a belief that is completely mistaken and unfounded, in light of God's nature.
A massive collection of CONSISTENT logical conclusions will be made based on it. And all of these conclusion together will form the appearance of what seems like a completely consistent internal coherence. It will STILL all seems to "fit together". A clear "picture" will form. There won't appear to be any contradictions. And any steps necessary to keep the premise valid will be made, regardless of the extent to which that means changing the meaning of the course.
Everything it says will be interpreted through that lens and filter. And the person will end up with a very elaborate, consistent, highly polished, internally supportive, self un-contradictory, and seemingly highly sensible set of conclusions. And it will all seem TRUE because it seems to make sense. And they will marvel at the seeming beauty of its logical harmony. BUT, the entire thing will be bullshit, because it all starts out with a false premise. And so the entire system of thought is completely mistaken. Yet it is regarded as truth because of its consistency.
You have to therefore be careful that your reasoning begins with something which is absolutely true. You need to understand God's nature first. And when you reason based on the truth, you will end up with truthful and valid and consistent answers, which are correct. You can't start with the world and try to reason backwards to find the truth. You have to start at the beginning of the system.
You have to have an awareness or grasp of what the absolute truth IS FIRST, before you can even proceed to think about anything. If you set off on the wrong foot, every conclusion you come to will be potentially false. But most of us will start out with false conclusions and assumptions and not question them, resulting in more false conclusions. Because we're starting out exploring all this with our egos, which has taken a whole bunch of assumptions as true, and this has not yet been questioned.
We have to find out first what the premise of our entire thinking is, whether we have started out on the wrong foot or not. And for that you have to ask yourself, what is the ultimate truth really like? What is God like? What is his nature? What IS the ultimate absolute premise? Where DID everything actually start, and what is the logical nature of that premise? Because from God, everything real proceeds as a logical system of thought, and it proceeds only according to His nature, and nothing can come from it which is unlike its starting point. So you have to be REALLY clear about God's nature before you can reason anything correctly.
When you can understand what God is like, you can start to draw truthful conclusions. And if you are careful, you can be GUARANTEED that these conclusions will be true. But if you do not understand God's premise, or you have difficulty being impeccable with your logic, then you will come to false conclusions because you'll be starting out with something false. And yet these conclusions will see true to you and make sense, even though they are mistakes or errors in reasoning. And you can end up with a whole lot of "it makes sense" even if you start out with lies.
This is happening A LOT in ACIM circles because many students are not yet in a position to grasp the nature of God's system, the premise of reality and the one truth. And so most of us are struggling to come to terms with what the conclusions are, yet alone being able to grasp where it all started or what it's all based on. And a lot of time is spent trying to uncover or learn about the premise.
If you return to the highest possible starting point, the pre-separation system, and you look at how God functions, and then you begin to reason out what CAME from that premise, and if you do so impeccably logically, you WILL come to true conclusions. But if you are mistaken about God, you will be mistaken in everything you conclude.
Those true conclusions will not only show you the things God COULD do, it will also show you what he COULD NOT do. What CAN come from Him, and what cannot. What He would will, and what he would not. And thus what you are, what your nature is, and what you are capable of in reality. When you do that, you'll see why the ego's system is entirely a FALSE premise, and EVERYTHING that comes from it will be false. And that includes the attempt to oppose God's premise, to overthrow the Kingdom, to make another world (including Earth), and why Earth CANNOT have come from God due to its nature being a complete contradiction of God's nature.
God does not make contradictions because He is logically consistent. For Him, heaven is the natural outcome of His premise. And Heaven is the ONLY outcome of His premise. Nothing else CAN come from it because it is rooted in truth. And because of His nature, Heaven HAD to be created. It's in God's nature to extend His logical premise to produce The Kingdom. Which is why it has always existed.
Earth, which is OPPOSITE to heaven in *EVERY* way, CANNOT COME FROM GOD. Its nature is opposite to His premise. It does not function like Him. It does not begin with the premise He begins with. And it cannot be a natural outcome of His thought system. If He were to create it, in addition to creating Heaven, that would mean two entirely different and opposing outcomes can result from a single premise. This is logically IMPOSSIBLE regardless of what the premise is. Each premise produces ONE conclusion in accord with it, not two different ones.
God could only create one or the other, and which one is set up in his beginning nature. Since Earth is opposite to Heaven, God could NOT have created it, otherwise He would have to have STARTED OUT with a split mind and be opposing himself. He would have to be fundamentally contradictory, as a premise, in order to PRODUCE two contradictory outputs. He could only Create ONE or the other, not both, and they cannot both exist or "be one" because of their contradictory natures. If Earth is real, heaven does not exist at all.
God is NOT contradictory, so He can ONLY produce ONE outcome. That outcome is HEAVEN, and Earth is therefore NOT OF GOD, and is not based on truth or reality. And since God is real, Earth therefore, logically, cannot be real. And since only what God creates CAN exist, Earth does not exist at all. And if God is permanent, Earth cannot be permanent. And if God exists, having Created ONLY heaven, Earth cannot exist at all. This is why "there is no world" and God did not create it.
"The world you see is an illusion of a world. God did not create it, for what He creates MUST be eternal AS HIMSELF" is a logical statement. Since Earth is NOT eternal, it must have come from a NON-ETERNAL premise, and since God is eternal, it cannot have come from HIS premise. And because HIS premise is true, it must have come from a FALSE premise. And therefore Earth is an illusion, and never will it be His one outcome.
"Heaven remains your one alternative to this strange world you made and all its ways; its shifting patterns and uncertain goals, its painful pleasures and its tragic joys. God made no contradictions. What denies its own existence and attacks itself is not of Him. He did not make two minds, with Heaven as the glad effect of one, and earth the other's sorry outcome which is Heaven's opposite in every way."