"The days of our years are threescore years and ten;
and if by reason of strength they be fourscore years,
yet is their strength labor and sorrow;
for it is soon cut off, and we fly away." (Psalms 90)
"Threescore years and ten." Yes, I am a septuagenarian. And I love that word. It has dignity, "gravitas," and solidity. Yes, and biblical imprimatur.
I'm blessed to come to the marker of my biblical allotment pretty healthy, physically fit, and reasonably mentally sound. At least for the moment. Ah, the moment! Septuaganarianism highlights in neon, moment after moment. Perhaps I'll attain a "four score." That decision is above my pay grade.
A decade or so ago, I had a close friend who was a decade or so older. At the time, she had what I thought was a curious habit or maybe a "quirk." She was physically healthy and fit. She had no hearing deficiency. Yet, when I spoke to her, her mouth would subtly move as though she were repeating my words to herself. Or, some part of herself was repeating to herself. Of course, I never mentioned my observation to her. Instead, I filed it away as interesting.
Now that I am a decade older and my dear friend is gone, I notice quirks in my behavior. Elders will recognize themselves in this scenario. I purposefully enter a room and suddenly forget my purpose.
And here's the theme of my discussion. I find myself talking to myself out loud. Note, I said TALKING TO MYSELF. But worse, I also answer myself like a 2nd person talking back. Why did YOU come in here? What was it YOU intended, needed, or hoped to accomplish? A discussion ensues. Heck, I don't know! REALLY? YOU'RE getting to be a doddering septuagenarian!
Before the conversation becomes too heated, I stop, center myself, breathe, focus, and sometimes recall my purpose. And if I don't, I laugh or growl, depending on my mood. And that is my point. At whom do I laugh? At whom do I growl? At me? At that other me? At both? At neither? At the cosmos? WHO IS WHO?
Fun wordplay, yet, it's serious. It's at least as serious as this seemingly "funny" Zen story:
Two monks were watching a flag flapping in the wind. One said to the other: The flag is moving.
The other replied the wind is moving.
[Master] Huineng overheard this. He said:
Not the flag,
not the wind;
mind is moving." 
Zen Buddhism and, frankly, a few other venerable spiritual traditions assert or infer that everything humans perceive is a construct of the mind. Our rationality dices an immeasurable infinity of Creation into a few finite bits digestible to each of us.
Who walks whom? 
Who acts? Who reacts? Is what we perceive real? It doesn't matter. What matters is that all of it is mind. With our minds, we sense, experience, participate in, and negotiate our day-to-day living. It's all useful. Mechanically, it works.
Spiritually, it's more than that. Spiritually, it's urgent to look beyond the mind and mechanics. Who walks whom? Who speaks to whom? Who listens to whom? WHO IS WHO? AND, WHO IS?
TO BE is the root of language and communication. Conjugating TO BE, we come immediately to I WAS, I AM, and I WILL BE. All our common linear perceptions of past, present, and future. WILL I attain fourscore in a decade? WILL I dodder less than I did at threescore and ten? Whatever, I will have been blessed to surpass the biblical imprimatur. But, again, that decision is above my pay grade. TO BE . . .
"I am that I am." (Exodus 3:14)
This is the God of the Old Testament, making HIS eternal nature understandable to Moses and the Israelites. He WAS, IS, or WOULD BE whatever they needed Him.
What WAS? What IS beyond our calculating minds?
Finite bits of Creation are a fraction of Creation. But, hey, do the math! There is much more to this than meets the eye of the human intellect. The great Catholic cleric Meister Eckhart wrote:
"The eye through which I see God is the same eye through which God sees me; my eye and God's eye are one eye, one seeing, one knowing, one love."
This is a matter of NO MIND! With no mind, we perceive what is. See mind! See, no mind! See that which is in between. See that which merges the two into one and both into none. See that which came infinitely before.
"Cease practice based
On intellectual understanding,
Pursuing words and
Following after speech.
Learn the backward
Step that turns
Your light inward
To illuminate within.
Body and mind of themselves
Will drop away
And your original face will be manifest." 
Zen Buddhist Master Dogen references a venerable koan. In Zen Buddhism, a koan is an adjudication, a judgment, a pronouncement, or a decision. Indeed, a koan cuts through dichotomy and lands at the ultimate truth.
A version of the oft-cited koan:
"Show me your original face before you were born."
"Without thinking of good or evil, show me your original face before your mother and father were born."
And another from the American novelist and short story writer Nathaniel Hawthorne :
"No man, for any considerable period, can wear one face to himself and another to the multitude without finally getting bewildered as to which may be true." 
I borrowed from an essay cited below:
"Hey, how can I have a face, or exist, before I was born?" or "Hey, I don't believe in evolution." But it is a question of "Who am I without my set of beliefs or my image of myself or an identity that I've adopted for myself?" 
Sit with this:
Who is Who?
 Huineng is acknowledged as the 6th Patriarch of Chinese Cha'n, or Zen Buddhism, in the Japanese tradition.
 My own observation from the front window of my house.
 Dogen Kigen (1200-1253) is the founder of Japanese Soto Zen Buddhism.
 Nathaniel Hawthorne (1804-1864)