Yoga Sutra 4.20 it takes some instants to discriminate objects,
Sūtra IV.20
They cannot both be clearly ascertained at the same time
They cannot both be clearly ascertained at the same time, for it takes some instants to discriminate objects, and it is not reasonable that it should then be discriminating oneself. Then again, when it clearly ascertains oneself, it is not then turned to objects, because it would take several instants to discriminate the self.
(Opponent) There is just a single discrimination – of both.
(Answer) No, because a discrimination has no parts. A mental operation which has no parts cannot reasonably illumine a number of things, as a light does. The light has different parts (rays), and so it can light up a number of things. But even our opponents do not think that knowledge has parts.
Further, acceptance that a single knowledge in a single instant should determine both, entails differentiation of action and agency. The determination of the two is an action, and what causes it is an agency.
It is not reasonable that there should be determination of both itself and another in a single instant, as the theorist of instants (kṣaṇa-vādin) holds, for he maintains that the origin of anything is itself action and is itself the agency.
Why is it not reasonable that there should be determination of both itself and another in a single instant, as the theorist of Instants (kṣaṇa-vādin) holds? It is said by him, to establish his doctrine of Instants, that the origin of anything its coming into being is itself action and is itself the agency. This is his position. (But) differentiation of action and agency will shatter the doctrine that they are one instant, because the action-instant would have to be established by an agency.
(Opponent) There can be this view: an idea, naturally perishing (along with its instant), is known by another idea immediately afterwards in the same stream of instants.
(Opponent) There can be this view of some of us: an idea (buddhi) naturally perishing (along with its instant) being extremely fragile, it perishes as it comes into existence, is known by another idea coming into being immediately afterwards in the same stream of instants, so that here the assumption of a permanently abiding Puruṣa is quite needless.
(Answer) The answer is: