Koan means a statment to cause spiritual awakening or insight in Zen Buddhism but had persisted even before in Indian scriptures.
Koans remind us the futility of intellectual pursuit and its limitations.
Koan is neither a riddle or a wise remark but it teases the mind with a doubt , injects the thinker with illogic and paralyses the intellect but yet pushes the self beyond these conventional limits of underrstanding and kindles a deep awakening within.
Koan is a contradiction, it is non conceptualization, it is something to be surpassed, like a ladder which is used and kicked out when it is not needed and forgetting you used one to climb up.
Koan induces the absolute experience of being in the now and being aware of the subtle truth of every action and living to understand ourseleves better.
The idea of Koan is to break every aspect of Non Duality, thus every ratioal approach of cause and effect, good and bad, right and wrong, real and false is duality and division and cant be the truth which is beyond these and thereby beyond the intellectual process of reasoning, is infact its essence.
"[Atman] though sitting still travels far. though lying down goes everywhere" - katha Upanishad.
" In the Ocean of Absolute Bliss what is there to be accepted or rejected, what else is there other than self, what is distinct from it ?" - Vivekachudamini of Shankara
"Iam the goal, Iam the support.
Iam the worship, Iam the sacrifice
Iam the Lord, Iam the witness
Iam the source, Iam the refuge
Iam the origin, Iam the disollution
Iam immortality, Iam the perishable"
from different passages of Bhagvad Gita by krishna
"Atman, smaller than the small, greater than the great, is hidden in the hearts of all living creatures" - Katha Upanishad
"What is here, the same is there and what is there, the same is here" - Katha