The scale of (causal) subtlety of objects ends in pradhāna
In the case of an atom of earth, the subtle element (tan-mātra) of odour is a subtler (causal) object (for the vicāra meditations); in the case of water it is the subtle element of taste; in the case of fire, light; in the case of air, touch; of space, it is the subtle element of sound. Subtler than these is the cosmic I (ahaṅkāra), and subtler than that is the Great Principle (liṅga); more subtle than that is pradhāna (a-liṅga – uncreated nature). There is nothing more subtle beyond pradhāna. (But) surely Puruṣa is at the limit of subtlety? Indeed it is, but it is not a subtle cause of the Great Principle in the same way that pradhāna is. Puruṣa is not the cause which produces it; it is only a cause which sets in motion. Hence the limit of subtlety is described as pradhāna (the ultimate cause).
In the case of an atom of earth, the subtle element of odour is a subtler (causal) object. When the atom of earth is analysed, it is found that the subtle element (tanmātra) of odour alone is its very essence. And the essence of the subtle element of odour has the liṅga, the principle called the Great, as its subtle cause.
The word liṅga (literally, having origination, and therefore destruction) carries the meaning that the subtle elements, which together with the cosmic I (ahaṅkāra) have come forth from the pure liṅga, the Great, go (ga) to dissolution (li) in it, and again that they come back from dissolution, from the pradhāna. Pradhāna, on the contrary, being a-liṅga (without liṅga or origination) neither goes to dissolution in anything else nor comes back. Of the Great, the pure liṅga, the subtle cause is pradhāna, the a-liṅga.
(Opponent) Surely Puruṣa is at the limit of subtlety too, so where does it come in this progression of ever more subtle causes?
(Answer) This objection is raised on the basis of a certain theory that Puruṣa too is a cause, but our position is not touched by it. The subtlety of the a-liṅga lies in the fact that it has no liṅga or origin but is the cause of the origin of the liṅga or Great principle. The point is that whatever is the cause of some effect is relatively more subtle than that effect. The objection raised is, that Puruṣa too is essentially without liṅga or origin. This is true, but Puruṣa is not more subtle than the liṅga in this special sense of being the cause of it. Puruṣa, though it is indeed without liṅga, is not the material cause of the liṅga principle, the Great, which is thus not its effect. Pure consciousness (caitanya) cannot be correlated with any effect.
If it could be so correlated, Puruṣa would necessarily also be something experienced, and would thus be for-the-sake-of-another, and would be essentially pleasure and pain and delusion. Moreover pradhāna would no longer be the cause of everything. This would go against all the evidence, and so he says that Puruṣa is only a cause (hetu) in the sense that its presence as experiencer sets pradhāna in motion. This is the meaning of the statement that subtlety reaches the limit with pradhāna.