Yoga Sutra 4.18 to the Lord mental processes are always known.

Sūtra IV.18

To Him, the Lord, the mental processes are always known, from the fact of the unchangeability of Puruṣa

To Him, the Lord, Puruṣa, the mental processes are always known. There is direct perception of them, and it is unquestionable that they are always known as objects. Again, the mental processes, as directly perceivable, are in fact remembered as having been known directly, like a jar, and not on the basis of authority or of inference. In the same way their form is known exactly, and they are never objects of uncertainty. If the mental process were never directly perceived, then like outer objects, some of them would appear uncertain at some time. But never are any of them found to be in the realm of uncertainty.

(Opponent) Still, if an object is known at any time at all, it is said to be known.

(Answer) No mental process can occur which is not known by direct perception. Nor could one be inferred from a result, because it could not be determined what the result should be.

Since what is uncertain cannot be an object, and the mental processes are remembered purely as themselves, regardless of any object, they are always directly perceived. They are the perceiver’s illuminator, instrument and manifestor, like a light. It is not that there is uncertainty (in perception) by the eye or other sense organ; there too there is direct perception. As things like jars are known by the special illumination of a light, so sounds are known through the ear by a special ‘light’ of its own, and so with the other senses and their objects.

And it cannot be argued that because this is not known in isolation, that is not a case of direct perception. The rays from two lamps are inseparably mingled with each other, and cannot be isolated as ‘this ray is this one’s, and that ray is that one’s’, yet we do not say that there is therefore no direct perception of them. In the same way here, a sense like the eye has a reciprocal relation with the external light which corresponds to it, and they are not known in isolation; but we cannot say simply on that ground that there is no direct perception. He who denies that the mental process must inevitably be directly perceived would surely deny himself too, for all perception depends on some mental process, and the ‘light’ of a perception of form depends on some idea.

And so he says: To Him, Puruṣa, the mental processes are always known, from the fact of the unchangeability of Puruṣa. That unchangeability is inherently eternal awareness, so it follows that they are always known as an object.

If Puruṣa were to change like the mind, then His objects the mental processes would be objects like those of the mind such as sound, which are known and also unknown. The knownness and unknownness of universals such as sound should be understood as changes of the changing mind; in the same way, the knownness or unknownness of the objects of the senses correspond to changes of the senses. But not even one of the mental processes is sometimes known and sometimes unknown, for they are invariably nothing but known. And so The unchangeability of the Lord, Puruṣa, entails the perpetual knownness of the mind as process.

The proposition is, that Puruṣa is unchanging; the reason is, that its objects are always known; the example of the contrary is, mind and senses. Because we are dealing with a perceiver of objects, examples like freed Selves do not serve to refute the point that Puruṣa’s objects are always known, because a freed Self does not have any objects.

(Opponent) There may be this possibility: mind alone, as both perceived and perceiver will illumine itself and also illumine the object. For mental processes themselves are self-cognized forms; they are like a lamp which causes to shine both jars and other things as well as itself. Why should any Puruṣa be supposed, outside the mind, as a perceiver of the mental processes?

(Answer) The reply to this is: