One is a verb
The word Advaita literally means 'not two'. Two is duality. I, and a separate world. Advaita is the teaching of non-separation. In Dutch they say 'van de een komt het ander', 'from the one comes the other'. So, before we can say two, we have to be able to say one. The number one begins the counting process.
If you look in a dictionary you will see that the word 'one' is classified as a noun or pronoun.
I would like to make it clear to you that it is in fact a verb, One'ing. Understanding that will make many other things clear.
Once upon a time you were a little baby and the apple of your parent's eyes because you were so cute, (you looked just like them), and so smart, and they wanted very much to turn you into a human being with all the appropriate capacities like walking, talking, going to the toilet all by yourself, and counting. They carried you down the stairs and counted the steps, one, two, three, etc. Or Papa held up some fingers and asked you 'how many?' (They still do that with drunks and pathological cases I think).
Mama used to play a little game with your edible toes, this little piggy went to market, this little pig stayed home, etc. Little by little your body parts were labeled and counted so you 'knew' that you have one nose, two ears, two arms, etc. The process of counting began with your very body.
All of this took place in the undifferentiated consciousness that you were. Little by little you were able to differentiate, first Mama and Papa and gradually other things like cats, and sisters.
What you learned with Papa on the stairs was a list of sounds. One, two three uno, dos, tres And they were very proud if you could get up to five or six without making any mistakes because basically the list is arbitrary.. In India it is ek, do, teen, char, panch. It could just as well be oble, goble, gooey, luk.. Again, at this point it is only a list of sounds. That is not yet counting. Another list of sounds is the alphabet: a, b, c, etc. but we do not associate that with how many of something we have. We don't say I have t pairs of socks. But we could in another system.
The first step towards counting is separating, differentiating, focusing on something to the exclusion of everything else. If you imagine yourself to be on Venus looking at a totally strange scene that you have never seen before, you might not be able to tell where something begins and something else ends. That is not so difficult to imagine I think.
In computer language this first step is 'selecting'. It is isolating, seeing as separate, pointing. Only after performing this activity can we say something like there are 'three' eggs on the table. The table has 'four' legs and so on. To count larger amounts we have to go through the process of separating and naming repeatedly until all that we wanted to count is exhausted. To count seventeen of something (unless you are Dustin Hoffman in the Rainman) you have to go point-one, point-two, point-three, etc, until you come to point-seventeen.
If this is all clear now I would like to say that counting is the act of one'ing over and over. And one'ing is the act of separating, thus of creating duality where there was unity. I'm not saying that this is bad in and of itself. In fact it is necessary and utilitarian, ordering three cups of coffee would be very difficult without it. It is convenient, but not the reality.
Learning this one'ing you also learned to consider yourself as separate from the whole. Counting began with your very body. Some primitive tribes count up to nineteen on fingers and toes and twenty is called 'the whole Indian'.
I hope that it is also clear that this one'ing is a verb, an activity, only you learned it so long ago and so deeply that you do not remember that it is an activity and it all happens automatically. But in fact if I ask you to find one of something now you will first select it with your vision. And so the act of one'ing is also the act of objectifying, of creating separate objects. It is a verb.
Taking one to be noun has certain consequences. It creates a static world in which process is forgotten. It creates a world in which you begin to think of yourself as a noun, with describable qualities. It is part of the forgetting of who we really are. Remembering that we are a process, a verb, and not a static thing, a one, is also remembering the wonder that we are, and that we are being lived.
We have been taught, at least in our Western culture that we are separate. Advaita tries in every possible way to remind us of our unity, that the one that we take ourselves mistakenly to be is in fact the whole. The whole is the only thing that has the right to be called One. And it is so in many religions. The One. The Absolute. When you were taught to count you were also subtly taught to objectify your body, as you also learned to objectify the cat and your sister and your little red car. Remembering that you are 'objectifying', 'one'ing' seems to very difficult, you learned it like bike riding, hard to forget. Try doing it deliberately, taking the automatic out of it. It may help to remind you that you are the Consciousness selecting.