The Heart Sutra embodies the natural extension of the Four Noble Truths in the reverse direction; it reminds us that the Four Noble Truths are essentially empty, transparent, not absolute truths. ‘Suffering’ is a relative truth, but it is noble because it leads to liberation. Sometimes people faithfully say, ‘Everything is suffering’ as if dukkha was an absolute truth, but that’s not what the Buddha was teaching. The Heart Sutra states:
‘Śāriputra!
Form is emptiness, emptiness is form.
Form is not separate from emptiness.
Emptiness is not separate from form.
So too feelings, perceptions, mental formations and consciousness …
‘There is no suffering,
there is no origin of suffering,
there is no cessation of suffering,
there is no Way;
there is no understanding and no attaining
for there is nothing to attain.’
The sutra thus takes the words of the Four Noble Truths and from the transcendent perspective empties them all out. Ultimately there is no dukkha. We think we’re suffering, but in ultimate reality we’re not – actually there isn’t any dukkha.
The Pali tradition encapsulates both of these implications. On the one hand it extends out from the personal to include all beings; on the other hand the noble yet relative quality of dukkha, its cause, its end and the way to its end are just empty appearances, like all other conditioned phenomena.
These Northern teachings of the Four Vast Vows of a Bodhisattva and the Heart Sutra endeavour to give voice to those particular dimensions of emptiness and altruism which were implied in the Pali, but were being lost because dukkha and its partner becoming were being held in a narrow, personal and overly concrete way. The Mahāyāna movement was an effort to balance things out.
https://www.amaravati.org/the-view-from-the-centre/