The twentieth yoga sutra speaks about the limitations of consciousness and the all-pervasiveness of the seer. The consciousness fails to comprehend the dualities of subject-object, observer-observed, or actor-witness simultaneously, while the seer can. Just as night and day cannot exist concurrently, similarly restlessness and restfulness can never co-exist. There always is a separation in the form of the light of the soul. This is the sudden arrival of enlightenment. In the third state of `the light of the soul`, wherein the consciousness is disseminated, and restlessness and restfulness fuse into the absolute consciousness. The seer, being eternal and changeless, is capable of perceiving both the waverings and the tranquility of the consciousness.

ekasamaye at the same time
ca and
ubhaya of both
anavadharanam cannot comprehend, cannot be held with affirmation or assurance

Consciousness cannot apprehend both the seer and itself at the same time.

It cannot comprehend subject-object, observer-observed, or actor-witness at the same time, whereas the seer can.

Day and night cannot exist simultaneously. In the same way, restlessness and restfulness cannot co-exist in absolute juxtaposition. In between night and day there is dawn. Likewise, there is space between the flow of restlessness, cittawtti or cittavahini, and restfulness, prasanta vrtti or prasanta vahirii.

In between these two rivers of restlessness and restfulness, and underneath them, flows the concealed invisible secret river - the river of the soul. This is dawn, or the sudden arrival of enlightenment.

For a yogi, restlessness is the night and restfulness is the day. In between, there is a third state which is neither day nor night, but dawn. It is the dispersion of consciousness, in which the rivers of restlessness and restfulness unite in the seat of absolute consciousness.

When the water of a lake is tranquil, the reflection of the moon on its surface is crystal clear. Similarly, when the lake of consciousness is serene, consciousness disperses itself. This is known as a glimpse, or a reflection of the soul.

The seer, being constant and unchangeable, can perceive the fluctuations as well as the serenity of consciousness. If consciousness itself were self-luminous, it too could be the knower and the knowable. As it does not possess the power to be both, a wise yogi disciplines it, so that he may be alive to the light of the soul.

It is stated in the Bhagavad Gita (11.69) `One who is self-controlled is awake when it appears night to all other beings, and what appears to him as night keeps others awake`. A yogic sadhaka thus realises that when consciousness is active, the seer is asleep and when the seer is awake, it is night to the consciousness.

Similarly, in the Hatha Yoga Pradipika, the word ha is used to indicate the seer as the `sun`, which never fades, whereas tha represents consciousness as the `moon`, which eternally waxes and wanes.