How is consciousness measured? There is a sphere of infinite space and there is sphere of infinite consciousness.
It is easy to comprehend what is infinite space is but it is not clear what is meant by infinite consciousness?
Does it mean infinite history of experience?
Or does it mean infinite presence of sentient beings with consciousness?
In MN121 the Buddha explains his step by step method for achieving Liberation or Nirvana. This method relies on the gradual removal or abandonment or &quot;giving up&quot; of objects and any boundaries/limits, any separation, any division. First, the gross objects/limits/separation is removed, then medium-gross objects/limits/separation is abandoned, then subtle objects/limits/separation is &quot;given up&quot;, and this process of incremental iterative refinement is repeated and perfected all the way until Final Liberation.
This process can be compared with a loop in a software program, a cycle:
var A = AttendTo(any object);
repeat until(A==Nirvana){
    var notA = FindComplement(A);
    A = AttendTo(A + notA);
}

On each iteration of this loop our current object is A. Next, we find its counterpart, the NOT A. Next, we combine the total of A + NOT A and make that our new A. This is repeated until Nirvana.
The first step of that process is to start where you are. Let's say you are looking out of your window and see a parking lot with cars and people. When you focus on one of those people, that's an A. When you focus on another person, that's another A. Any single person or any car can be your object. Then you try to find the counterpart (or the mathematical complement) of that A, the NOT A. If you take one member of a mathematical set, then the complement is the rest of that set. If you take any one object (person or car) on the parking lot, then its complement is everything else on that parking lot except that first object. Next step is to put together A + NOT A and make that your new A. When we combine our first person with the rest of the parking lot, the resulting A = A + NOT A is &quot;the entire parking lot&quot;. This is the end of the first iteration.
The next iteration is when our A is &quot;the entire parking  lot&quot;. The NOT A is the rest of the world. The A + NOT A is &quot;the entire planet&quot;.
The next iteration is when our A is &quot;the entire planet&quot;. The NOT A is the rest of the universe. The A + NOT A is &quot;the Infinite Space&quot;. The reason it's called &quot;infinite&quot; or &quot;boundless&quot; or &quot;limitless&quot; is because it is spatially all-inclusive without any borders or separation. It is our first serious attempt at attaining an undivided meditation object.
The next iteration is when our A is &quot;the Infinite Space&quot;. This is where it gets a bit more tricky. What is the NOT A, what is the complement of the Infinite Space in an even broader context? Can we expand from the Infinite Space even further out? In other words, if the A of Infinite Space is one member of a larger set, then what could those other members be?
(...drum roll...)
The other members are all other phenomena, all other contents of our consciousness! Then A = A + NOT A is the entire consciousness with the entire totality of all its possible states and objects. When this becomes our new A, our new object of our iterative meditation refinement process, this stage is called &quot;The Infinite Consciousness&quot;. Again, the reason it is called &quot;infinite&quot; or &quot;limitless&quot; or &quot;unbounded&quot; is because it is our new standard of all-inclusive undivided object of meditation.
The next iteration of this goes as follows. If A is The Infinite Consciousness, then what is its counterpart? What is beyond all phenomena, beyond all states of mind, all contents of consciousness? It is the complete absence of any content, complete Nothingness. This is our NOT A. And what is the superset of both A and NOT A? It is that which includes both &quot;entire realm of conscious experience, with all its possible states&quot; and &quot;the complete absence of anything&quot;. This A + NOT A is called &quot;the realm of neither (just) perception nor (just) nonperception&quot;, in other words it is the common ground for both consciousness and nothingness. But what is it, really? It is the point of view that comprehends all conscious experience as well as comprehends nothingness. It is the ultimate reference point.
Finally, taking this last object as an A, we need to work harder to find its complement. Could there be anything beyond the ultimate reference point that comprehends both consciousness and nothingness? It seems impossible to imagine. However, if you look very-very carefully you can realize that this ultimate reference point is nothing but a sign of &quot;I&quot;, the sign of &quot;subject&quot;. The complement of that A is complete cessation of I-making, complete cessation of being a point of view. Which means, it is complete cessation of interpretation, evaluation, discernment, and recognition, complete cessation of semiosis. This NOT A of &quot;neither perception nor non-perception&quot; is traditionally known as &quot;cessation of perception and feeling&quot;. And if we combine these A + NOT A, that is if we find the common ground of both, then finally we are done.