A wave is shaped water. Water is not wave dependent. Whether waves arise or do not arise does not affect the water. Drawing from this, in Buddhism, we can say that thought is shaped spirit, spirit being shapeless and luminous. In no way is spirit dependent upon thought. On the same track, we can say that the word “spirit” is not spirit. It is just a signifier/sign — not the signified. The signified is yet to be personally known.
It follows from this according to verse 277 in the Dhammapada, that all (sabbe) shapes (saṅkhāra) are impermanent (anicca). Then we learn in verse 278 that all shapes are suffering (dukkha).
It logically follows from this that shapes are not permanent. Any shape or aggregation such as the five aggregates of form, feeling, perception, volition, and consciousness are never permanent or eternal. Then in verse 383 it says, having known (ñatvā) the dissolution of [all] shapes, a knower of the unmade (akataññū) are you, O Brāhmin. Logically, our Brāhmin is also a knower of the shapeless eternal!
Beings, it would seem, are victims of their own ignorance and inability to distinguished between shapes and that or spirit from which shapes are made. Even the finest thoughts or thought cannot unshape itself to reveal what it is made from. Speculating on what is unmade is to be on a fool’s errand. There is another process, one of abandonment— Zen's own via negativa. Zen master Sixin Wuxin said it best.
"While still alive, be therefore assiduous in practising Dhyāna. The practice consists in abandonments. ‘The abandonment of what?’ you may ask. Abandon your four elements (bhuta), abandon your five aggregates (skandha), abandon all the workings of your relative consciousness (karmavijnana), which you have been cherishing since eternity; retire within your inner being and see into the reason of it. As your self-reflection grows deeper and deeper, the moment will surely come upon you when the spiritual flower will suddenly burst into bloom, illuminating the entire universe. The experience is incommunicable, though you yourselves know perfectly well what it is."
This practice begins by living far away from the madding crowd and overcoming the five hindrances. All the theoretical knowledge that we have gained it not going to help us. It our retreat it will become, over time, an impediment. It is a life of shape identification without ever meeting, face to face, what the countless shapes are actually composed from. On such a foolish journey, one will never become a knower of the unmade.