here's a simple koan: there sits a goose in a glass bottle. the opening is too small for the goose to get out. how do you get the goose out of the bottle without killing the goose or breaking the bottle?
before you try to think of an answer, think about this.
an answer only exists in relation to a question, and a question only exists in relation to our self. if our self doesn't exist, then neither does an answer or a question.
if a question can not be answered with dualistic thought, then what? throw it out! the truth lies beyond logic. think about the question, why does there need to be an answer? because you think a question exists and therefore there must be an answer. but what if you didn't see a question? or what if you saw so many questions that the question ceased to be a question! because questions as well as their answers are relative. it's kind of like saying the same word over and over again. it begins to sound strange, because words only have meaning in relation to other words.
now let's get deep.
a koan can not be answered with an "answer." a koan must be answered with direct understanding of the situation. and that situation is one where all things and thoughts in space and time become one.
it is only in our mind that anything is separated into opposing pieces. it is only in our mind that we create rules by which these pieces must act. for every "right" answer there is a "wrong" answer. and by these rules of right and wrong, we live and die. so if rules aren't rules until we think of them as such, what are rules before they're rules? certainly they always exist in some form, for we can not have the universe without the law of gravity. right?
this answer - "it" just "is."
and if it weren't? it wouldn't be!
could it be nothing? yes, within the concept that nothing is everything. but how is that possible?
it is only when your mind choses to include or exclude something from another that space and time exist. if hypothetically, you heard all frequencies of sound at the same time, do you think you would be able to discern one from another? now, what if you heard them from the day you were born to the day you died? and they never wavered in pitch or volume with not a moment of silence in between. would you hear anything?
and so everything becomes nothing.
this is the realm of zen enlightenment. this is where the line between dualities begins to blur, and eventually disappears altogether.
this is the answer to every koan, ever.