This Self is unmanifest, since it is not made manifest by any instrument. For that very reason it is unthinkable: what is within the range of the senses becomes an object of thought, but the Self, being beyond the range of the senses, is unthinkable. And for that reason it is unmodifiable: as milk is modified by curd-ferment into another form, the Self is not so modified; being partless, it is changeless, for nothing partless is seen to be of a nature to be modified. Therefore, knowing the Self in the manner described, you should not grieve, thinking 'I am the slayer of these' or 'these are slain by me'. Granting, for argument's sake, that the Self is not eternal, this is said.

By the means of knowledge through which things fit to be cut and the rest are made manifest, this self is not made manifest; so it is 'unmanifest', and therefore of a kind other than the cuttable and the rest. And it is 'unthinkable', for, being of a kind other than every thing, it cannot even be thought of as joined with the natures of those things. And for that reason it is 'unchangeable', not liable to change. Therefore, knowing this self of the character described, you ought not to grieve on its account.

This is a brief sub-gloss. For a fuller reading of this verse, see Madhusūdana, Śaṅkara, or Rāmānuja above.

It is for this very reason that the self is described as unmanifest and the rest.