This is a very good thread. I am a Buddhist and I have some thoughts about how the No-thingness card slots in for the Hierophant. I read somewhere that the Hierophant represents the synthesis and resolution of the eternal inner question: what is the meaning of life? And that the word Hierophant means 'revealer of secret things.'
I'm new to tarot, but I have learned that the Hierophant is taken to mean seeking after wisdom or enlightenment in spiritual matters, seeking guidance.
When seeking after the meaning of life, the Zen answer to that question is that there is no meaning--there is only life. Life itself is glory enough. All else is emptiness: shunyata. (Shunyata is a concept in Mahayana Buddhism which teaches that beings and things have no intrinsic existence in themselves. All phenomena come into being because of conditions created by other phenomena. Thus, they have no existence of their own and are empty of a permanent self. There is neither reality nor not-reality; only relativity.)
The concept of no-thingness (or emptiness, or shunyata) is a key theme in the Heart Sutra, which is considered the most succinct summation of Buddhist doctrine. Here it is (translated by Thich Nhat Hanh):
'The Bodhisattva Avalokita,
while moving in the deep course of Perfect Understanding,
shed light on the Five Skandhas and found them equally empty.
After this penetration, he overcame ill-being.
'Listen, Shariputra,
form is emptiness, and emptiness is form.
Form is not other than emptiness, emptiness is not other than form.
The same is true with feelings, perceptions, mental formations, and consciousness.
'Listen, Shariputra,
all dharmas are marked with emptiness.
They are neither produced nor destroyed,
neither defiled nor immaculate,
neither increasing nor decreasing.
Therefore in emptiness there is neither form, nor feelings, nor perceptions,
nor mental formations, nor consciousness.
No eye, or ear, or nose, or tongue, or body, or mind.
No form, no sound, no smell, no taste, no touch, no object of mind.
No realms of elements (from eyes to mind consciousness),
no interdependent origins and no extinction of them
(from ignorance to death and decay).
No ill-being, no cause of ill-being, no end of ill-being, and no path.
No understanding and no attainment.
'Because there is no attainment,
the Bodhisattvas, grounded in Perfect Understanding,
find no obstacles for their minds.
Having no obstacles, they overcome fear,
liberating themselves forever from illusion, realizing perfect nirvana.
All Buddhas in the past, present, and future,
thanks to this Perfect Understanding,
arrive at full, right, and universal enlightenment.
'Therefore one should know
that Perfect Understanding is the highest mantra, the unequaled mantra,
the destroyer of ill-being, the incorruptible truth.
A mantra of Prajñaparamita should therefore be proclaimed:
'Gate gate paragate parasamgate bodhi svaha
Gate gate paragate parasamgate bodhi svaha
Gate gate paragate parasamgate bodhi svaha.'
[The last 3 lines are a mantra that means basically, 'Over, over, all the way over, all the way over to the other shore to enlightenment, hurray.']
This is a very heavy thing to bring up on a tarot message board, but there you have the basis for the No-thingness card.
The Buddha discouraged questions such as 'What is the meaning of life?' What good do such questions do? They are not helpful. The Buddha taught that asking such questions is akin to a dying man demanding to know who shot him and why before he will allow the arrow to be removed from his heart. The card suggests that if you are seeking guidance from an outside source, an authority like the Hierophant, you are like that wounded man.
All of these concepts are contained in this one black card.