The core of the Heart Sutra is the ultimate truth of "emptiness" which is briefly mentioned as "「色不異空 空不異色 色即是空 空即是色」(Form is no other than emptiness, emptiness is no other than form. Form is namely emptiness, emptiness is namely form.)"
This is exactly the teaching of non-duality. Because we can transcend duality by understanding its deep meaning. If we assume "form" as "A" and "emptiness (other than A)" as "B", its logic will be "Because A is made of non-A elements (B), A is no other than B. Because B is made of non-B elements (A), B is no other than A. Therefore, A is equal to B and B is equal to A."
And non-duality helps us throw away all notions. If we suppose "form" as "body" and "emptiness (other than body)" as "the whole cosmos", the verse will be as follows:
1) Body is no other than the whole cosmos.
2) The whole cosmos is no other than body.
3) Body is namely the whole cosmos.
4) The whole cosmos is namely body.
And the cause of each verse will be as follows:
1') That's because body is made of non-body elements, namely
the whole cosmos. (Implicate order)
2') That's because the whole cosmos is made of non-whole
cosmos elements, namely body. (Implicate order)
3') That's because body and the whole cosmos are
interdependent co-arising. (Dependent origination)
4') That's because the whole cosmos and body are two sides of
the same coin. (Middle Way: not two but not one)
And if we suppose "body" as "separate existence" and "the whole cosmos" as "non-separate existence", the verse will be as follows:
1") Separate existence is no other than non-separate existence.
That's because separate existence is made of non-separate
existence.
2") Non-separate existence is no other than separate existence.
That's because non-separate existence is made of separate
existence.
3") Separate existence is namely non-separate existence. That's
because separate existence and non-separate existence are
interdependent co-arising.
4") Non-separate existence is namely separate existence. That's
because non-separate existence and separate existence are
two sides of the same coin.
Therefore, in the ultimate dimension, we don't need to separate sufferings from happiness, darkness from light, afflictions from enlightenment, death from birth, non-being from being, end from beginning, going from coming and otherness from sameness...etc. As a result, all notions are extinct. This is the wisdom of emptiness which enables us to transcend the duality and throw away all notions. If we understand this wisdom deeply, we will be able to rest in nirvana filled with perfect solidity and freedom without fear.
(cf. 1) http://www.slideshare.net/compassion5151/light-and-darkness
(cf. 2) http://www.slideshare.net/compassion5151/spiritual-ancestors
Hokkaido, Japan Photo by Ines iles