Shrishti (Creation) ,its reasons - explanation of Chhandogya Upanishad

Very interesting discussion, I stumbled upon today. The topic f discussion was, "What is the reason for Shrishti (Creation), what was before and what will be in the end"

Hearing this conversation, I forgot all my human issues, pain of failure, rejection & joys of achievement. I tried to explain, Indic (Sanatan) point of view.
With age, memory fails me often & I struggled to remember what I had read vaguely.

Sad (Sat) is the reason of Shrishti(शृष्टि) in karta as well as Kaaran (कारण ) roop (form)

शृष्टि और प्रलय क्रमिक रूप से चलते है! हम अवयक्त से शूक्ष्म और शूक्ष्म से शथूल मैं जाते हैं तो सृजन होता है और उल्टा जाते हैं तो प्रलय! 

sad eva, saumya, idam agra asid ekam evadvitiyam,
taddhaika ahu, asad evedam agra asId ekam evAdvitIyam,
tasmad asataH sat jayata 

Chandogya Upanishad 6.2.1

saumya: dear boy
idam: this (universe)
agre: in the beginning (before creation)
ekam: one
eva: only
advitIyam: without a second
sat: existence
eva: only
AsId: was
tad: about that
ekeha: some
Ahu: say
idam: this
agre: in the beginning
ekam: one
eva: only
advitIyam: without a second
asat: non-existence
eva: alone
asid: was
tasmad asat: from that non-existence
sat: whatever exists
jayet: arose (was born)


In the beginning, dear boy, there was existence alone,
one only without a second. Some people say that, in the
beginning, there was non-existence alone, one only without
a second. From that non-existence (they say), arose whatever
exists.


SAT (existence, truth): SAt is which is self-evident and
does not require any proof and does not need anything else
to exist. e.g. I exist irrespective of anything else and
this does not require a proof. Also, SAT is that which exists
the same in all three periods of time (past, present and
future) trikAla abadhitam satyam.

Now, let us look at world and creation. Creation is the name
(nAma) and form (rUpa) with qualities (guNa) in time (kAla)
and space (desha). That which exists before creation must be
nameless, formless and attributeless and not bound by time
and space. Such is SAT. SAT stands for that which is mere
existence, extremely subtle, all-pervading, ekam, pure
consciousness, and indivisible.

EVA (only): That which exists before creation of name and
forms must be beyond time and space and must be infinite.
There cannot be two infinities, and therefore SAT *alone* (eva)
existed before creation.

IDAM (this): The world that is experienced and known to us is
referred to as idam (compare with pUrNamadaH pUrNamidam). SAT is
adaH beyond purview of thought and cannot be known as this. Also,
SAT cannot be objectified by thoughts.

AGRE (before): We should recognize 'when', 'where', 'before' are
all time and space concepts and are parts of creation.

AsIt (was): The question can be raised why the word 'AsIt' (was)
was used here in the past tense. SAT is there even now and is ever
exstent, not only before creation. The word 'was' is used with
reference to our present experience of the world.

ekam eva advitIyam (one only without a second): i.e. it (SAT)
has no svajAtIyabheda (no generic difference, i.e. no difference
within the same species), no svagatabheda (no intrinsic difference,
i.e. no difference within one self), or no vijAtIyabheda (no extrinsic
difference, i.e. no difference between species). Thus, it (SAT) is
homogeneous, only one and without a second.

It is also suggested here, that some say that before creation
there was only non-existence and from that non-existence arose
existence. But, that idea is refuted in this and the next mantra.

Tat sat!