Haskell Moore: ..... No matter what you do it will never amount to anything more than a single drop in a limitless ocean.
Adam Ewing: What is an ocean but a multitude of drops?
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This instantly struck me as the central Kubrick theme of ASO, by ref
 to what he said to Playboy re "beyond the infinite" [to use the crass 
expression].
KUBRICK: I will say that the God concept is at the heart of 2001 but 
not any traditional, anthropomorphic image of God. I don't believe in 
any of Earth's monotheistic religions, but I do believe that one can 
construct an intriguing scientific definition of God, once you accept 
the fact that there are approximately 100 billion stars in our galaxy 
alone, that each star is a life-giving sun and that there are 
approximately 100 billion galaxies in just the visible universe. Given 
a planet in a stable orbit, not too hot and not too cold, and given a 
few billion years of chance chemical reactions created by the 
interaction of a sun's energy on the planet's chemicals, it's fairly 
certain that life in one form or another will eventually emerge. It's 
reasonable to assume that there must be, in fact, countless billions of 
such planets where biological life has arisen, and the odds of some 
proportion of such life developing intelligence are high. Now, the sun 
is by no means an old star, and its planets are mere children in cosmic 
age, so it seems likely that there are billions of planets in the 
universe not only where intelligent life is on a lower scale than man 
but other billions where it is approximately equal and others still 
where it is hundreds of thousands of millions of years in advance of 
us. When you think of the giant technological strides that man has made 
in a few millennia -- less than a microsecond in the chronology of the 
universe -- can you imagine the evolutionary development that much 
older life forms have taken? They may have progressed from biological
species, which are fragile shells for the mind at best, into immortal 
machine entities -- and then, over innumerable eons, they could emerge 
from the chrysalis of matter transformed into beings of pure energy and 
spirit. Their potentialities would be limitless and their intelligence 
ungraspable by humans.
At what he calls the basic [Clarke] level the movie shows a "long" 
advancement of man's "evolution" from ape to spaceman, and it seems most
 subscribe to that level, especially with the sudden appearance of 
Starchild like a Catholic Confession to "wipe the slate" of all the EVIL
 we see.
But the Kubrick level says that was just "a single drop" and 
logically there are "forms" out there [ie the God thing] that are so 
advanced that we can not possibly understand them [kinda following 
Darwin's attempt to explain the conception of time to the finite and 
limited human mind].
However Kubrick is saying it is not all doom & gloom and we must
 TRY to advance ourselves no matter how tiny that may be AND pass it on - hence the Zarathustra connection.
His quote is
"The most terrifying fact about the universe is not that it is hostile but that it is indifferent;
 but if we can come to terms with this indifference and accept the 
challenges of life within the boundaries of death — however mutable man 
may be able to make them — our existence as a species can have genuine 
meaning and fulfillment. However vast the darkness, we must supply our own light."
The break in the [eternal recurrence] chain during that one drop is 
cleverly shown by Moonwatcher making an incredible scientific system [a 
la Stonehenge] to predict solar eclipses AND passing it on to ape junior
 [a la Ishango] and finally passing it on to man via the "mutating bone"
 scene.
Then we see man get it totally wrong where a mission is concocted 
based on fraudulent evidence and it is [maybe thankfully] not passed on 
to any "space partners" and ends up a complete waste of space with good 
old Dave "dying alone, 100 years ago".
But then Kubrick throws in the Starchild with a new burst of 
Zarathustra to say "OK it was a huge stuff-up but at least America TRIED
 to supply its own light - just that egos and politics got in the way."