The secret of Zazen is the integrity and the dynamism of the spine; this is why we place such emphasis on posture.
If we sit correctly, with our pelvis at the right angle and our weight dropping down throughout sit bones, then the whole spine becomes dynamic. Our head is no longer a weight on our torso. It’s light and spacious, and our whole torso is integrated and experienced as a dynamic oneness rather than disparate parts. The spine is like an energetic central column.
The hand position that we have, with our little fingers resting between our navel and our pubic bone (depending upon the proportions of our body) broadly directs us to the right place, but I don’t think sufficiently. Our tendency with that mudra is to think that we breathe into our lower belly, which entails when we’re breathing in, our belly is going out.
That’s not quite right.
If our spine is in the correct position, it’s true that we’re breathing into our lower belly. But it doesn’t feel as if we’re breathing in our lower belly. Or not just there.
If our spine is in the correct position it opens up the whole space of awareness, as it were, behind and below our hands. The whole of our lower back and our pelvic floor, together with our lower belly, opens up. Specifically an area of awareness emerges which is, as it were, right within this pelvic bowl and experientially towards our front. Although it isn’t anatomically accurate to say this, it’s as if our spine is curving right down into the ground between our sit bones. We’re aware of the front of our spine and we can breathe into that general area.
I think this awareness, which you will need to experiment with yourself, is the key to understanding Dogen’s enigmatic definition of Zazen as being the dharma gate of ease and joy.
To understand ‘ease’ isn’t hard: it’s the equanimity that meditation, all sorts of meditation, promotes.
But ‘joy’ is something, I think, dependent upon our physicality—the integration of our body and the dynamism of our body, not pictured, not objectified, but experienced.