Verses on Sāṃkhya 4

Now, into how many kinds are these divided? To this, it is said: into four kinds. If it is asked: how? That is stated:

Root nature is not a modification; the seven beginning with the great [principle] are both natures and modifications;
but the sixteen-fold set is only a modification; the spirit is neither nature nor modification.

"Root nature" is primordial matter, because it is the root. "Root" means the source, the beginning of the seven that are both natures and modifications. It is nature (prakṛti) because it produces (prakaraṇa); it is nature because its property is generation. It is "not a modification"—an un-modification—because it is not originated from anything else. The meaning is that it is only a cause, not an effect, because it is unoriginated and an originator. But the seven beginning with the great [principle] are both natures and modifications: the great [principle], egoity, and the five subtle elements—these seven are natures by being the causes of other things, and themselves modifications by being effects. With respect to that, he explains the manifestation: from primordial matter arises the intellect, so it is a modification; and it produces egoity, so it is a nature. Egoity is originated from the great [principle], so it is a modification; it produces the subtle elements, so it is a nature. The subtle elements are originated from egoity, so all five are modifications; from them the five gross elements are born, so they are natures. Because they are originated and are originators, these seven are both natures and modifications. The subtle elements are those named sound, touch, form, taste, and smell. "The sixteen-fold set, however, is only a modification" because it is merely an effect; it has no nature-hood, because it is not a cause. He explains its manifestation: the eleven sense faculties originated from the modified egoity, and the five gross elements from the subtle elements—this sixteen-fold group is a modification originated from something else; the meaning is that nothing else is originated from it, because it is originated and is not an originator. But the spirit is not a nature, because it is not an originator, nor is it a modification, because it is not originated. The meaning is that it is neither cause nor effect. In this way, this fourfold division of nature and modification has been stated by virtue of the distinction: nature, nature-and-modification, modification, and neither nature nor modification.