[The notion of] conjunction is the means of understanding the real nature of the powers of the possessed and of the possessor.

Bryant Commentary:

Tying the verses in this chapter together, as touched upon in II.15, and echoing the Four Noble Truths of Buddhism, the theme of this second pāda (chapter) is suffering, the cause of suffering, the state beyond suffering, and the were dedicated to the immediate causes of suffering on a psychological level (the kleśas and their consequences); II.15 to the reality of suffering itself; II.16, to future suffering that can be avoided; II.17, to the cause of suffering on a metaphysical level as the union, saṁyoga, between the seer, draṣṭṛ, and the seen drśya; II.18–19, to the seen; II.20, to the seer and the state beyond suffering; and II.21–22, to the seen again. This sūtra through II.27 will deal with saṁyoga, union, the metaphysical cause of suffering, and saṁyoga’s removal, and the remainder of the chapter will be devoted to the means to accomplish this.

This sūtra was composed with the intention of explaining the nature of the conjunction, or association, saṁyoga, between prakṛti and puruṣa, says Vyāsa. Puruṣa is the possessor, svāmi, and he is conjoined with that which he possesses, sva, namely prakṛti and her objects (the seen of the previous sūtra), for the sake of experience. Worldly experience means perceiving the seen, and liberation means perceiving the real nature of the seer. Ignorance is the cause of the conjunction between the seer and the seen, and true knowledge dispels ignorance and is therefore the cause of liberation.

Strictly speaking, continues Vyāsa, true knowledge is not the real cause of liberation because when ignorance does not exist, bondage does not exist, and so technically it is this absence of ignorance that corresponds to liberation. It is because knowledge removes ignorance that it is said to be the cause of liberation, but it is actually the indirect cause of liberation. Vijñānabhikṣu points out that true knowledge, or discrimination, operates right up until the immediate moment prior to liberation. He reminds his readers that discrimination is still a product of the material intelligence, but full liberation involves complete separation between puruṣa and buddhi. This is the difference between sabīja and nirbīja samādhis.

With an eye on the next sūtra, Vyāsa turns his attention to different views on what constitutes ignorance—the synonym he uses for ignorance here is adarśana, the lack of perception (of the real nature of the puruṣa). He lists the following possibilities, which are further discussed by the commentators.

(1) Is ignorance the result of the play of the guṇas? This, says Hariharānanda, is correct insofar as ignorance continues for as long as the guṇas are active, but it doesn’t explain the cause of ignorance any more than heat in the body explains the cause of fever.

(2) Is ignorance due to the mind, which fails to modify itself into the true object of knowledge, that is, the knowledge of the distinction between puruṣa and prakṛti, even though this object is present before it? This possibility is of limited value, says Hariharānanda, like saying, “Illness means to be unwell.”

(3) Does ignorance spring from the guṇas, which fail to produce the true object of knowledge, namely, discrimination, even though this is latent within them? The same limitations from the previous option apply to this possibility. Another problem with this type of view, says Śaṅkara, is that since the guṇas are eternally in flux, if ignorance were a product of the guṇas, it too would be eternal and so there would be no liberation.

(4) Does ignorance remain dissolved as latent saṁskāras in the guṇas of prakṛti at the end of each creative cycle, becoming reactivated in the next creative cycle, at which time it produces an appropriate mind to serve as its substratum or container? This position, say the commentators, is acceptable to the Yoga school and is discussed further in the next sūtra, but it does not explain ignorance.

(5) Is ignorance the latent impetus that impels movement in prakṛti itself? The same objections apply here.

(6) Is it the very power and capability of prakṛti to reveal herself to puruṣa that is the ultimate cause of ignorance? This option, says Vijñānabhikṣu, is a variant of item 3. Vijñānabhikṣu quotes a charming verse from the Sā ṅkhya Kārikās (LXI) personifying prakṛti when her game is up and she has been seen by the enlightened puruṣa for what she is: “The other one [prakṛti] thinks ‘I have been seen!’”

(7) Is ignorance the characteristic of both prakṛti and puruṣa? Prakṛti is inert, lifeless matter, but its evolute buddhi appears to be ignorant due to being animated by the presence of puruṣa; likewise, puruṣa appears to be ignorant due to its awareness of buddhi, even though, in its pure state, it does not contain either ignorance or knowledge.45 It is only when the power behind knowledge contacts the objects of knowledge—when the consciousness of puruṣa shines on prakṛti and her manifestations—and is reflected back to puruṣa that ignorance is produced, so is ignorance the product of both? The problem with this, says Hariharānanda, is that it may be correct, but it doesn’t explain ignorance: It is like saying sight is dependent on the sun, which doesn’t explain sight.

(8) A final opinion is that ignorance is ultimately and paradoxically knowledge itself. To know, after all, is to know something. All things are prākṛtic. Therefore, knowledge of things occurs only when puruṣa is joined with prakṛti.

There are thus many views on ignorance, says Vyāsa. They all contain some element of truth. The common denominator of all them is the conjunction of puruṣa with the guṇas of prakṛti. Ultimately, the origin of ignorance remains mysterious in all Indic philosophical schools; indeed, it is considered beginningless, and thus the question of its origin is bypassed altogether. In the theistic schools, it is a power of Īśvara, God.

Alliance Is The Means Of Realising The True Nature Of The Object Of the Knower And Of The Owner, The Knower (i.e. The Sort Of Alliance Which Contributes To The Realisation Of The Seer And The Seen Is This Relationship)

It is by virtue of the apparent indivisibility of the phenomenal world and pure awareness that the former seems to possess the latter’s powers.

The association of the Owner with its possessions is for the purpose of obtaining the power of both and, through discrimination, realizing one’s essential nature.

The purpose of the coming together of the Purusa and Prakrti is gaining by the Purusa of the awareness of his true nature and the unfoldment of powers inherent in him and the Prakrti.

The conjunction of the seer with the seen is for the seer to discover his own true nature.

Iyengar Commentary: 

The powers of purusa and prakrti are intended for Self-Realization. The purpose of their contact is the unfolding of their inherent powers, and the seer’s discovery of his own essential nature.
This sutra makes clear that a desire for fusion or a close association or integration between the owner, the ‘owning’ and the owned has existed since the beginning of civilization. 

By the light of pure knowledge, the owner, the seer, perceives and cognizes whatever is to be perceived or cognized through his association with nature. If this association is fed by ignorance, it leads the master towards enjoyment, desire, and ailments, and binds him. But if non-attachment is developed, it leads to detachment or renunciation, vairagya.

If the master maintains constant watchful awareness of his consciousness, associates with nature without attachment and remains a witness, nature (prakrti) leads its owner, the soul, to freedom, moksa.”

The union of the Owner (Puruṣa) and Owned (Prakṛti) causes the recognition of the nature and powers of them both.

Satchidananda Commentary:

Saṁyoga (union) is necessary for the Puruṣa to realize itself with the help of nature. Saṁyoga means perfect union or junction. And here it doesn’t mean the union of the individual self with the higher Self, but the union of the Puruṣa and Prakṛti, Self and nature. When they are completely apart, they don’t express themselves. Their connection, however, lets us know them both. They help each other. It is something like if you want to print with white letters, you must have a black background for contrast. You can’t write white letters on a white background. Through the Prakṛti, we realize we are the Puruṣa. If not for the Prakṛti, we could not know ourselves. So Prakṛti isn’t just bondage as many people think. It is necessary.

Junction is the cause of the realisation of the nature of both the powers, the experienced and its Lord.

SV Commentary:

According to this aphorism, when this Soul comes into conjunction with nature, both the power of the Soul and the power of nature become manifest in this conjunction, and all these manifestations are thrown out. Ignorance is the cause of this conjunction. We see every day that the cause of our pain or pleasure is always our joining ourselves with the body. If I were perfectly certain that I am not this body, I should take no notice of heat and cold, or anything of the kind. This body is a combination. It is only a fiction to say that I have one body, you another, and the sun another. The whole universe is one ocean of matter, and you are the name of a little particle, and I of another, and the sun of another. We know that this matter is continuously changing, what is forming the sun one day, the next day may form the matter of our bodies.

This aphorism was composed for the purpose of explaining the nature of conjunction. ‘ Conjunction is that which brings about the recognition of the natures of the power of owning and the capacity of being owned.’ The Puru§a is the owner. ‘ The knowable * is whatever is owned. The former is conjoined to the latter for the purpose of knowing. The cognition of the knowable which follows from that conjunction is enjoyment. The knowledge, however, of the nature of the knower is emancipation. Conjunction, therefore, ends when it has caused knowledge. Knowledge is, therefore, called the cause of separation. Knowledge is the contracditory of ignorance. Therefore, ignorance is said to be the reason for conjunction. Here knowledge is not the cause of freedom (Moksa) ; because the absence of Ignorance itself, meaning as it does the absence of bondage, is freedom (Mok§a). When knowledge comes into existence, ignorance which is the cause of bondage disappears, and with it the bondage which is caused thereby. It is for this reason that knowledge, the seeing of the true nature of things, is said to be the cause of Kaivalya (absolute independence, standing alone.)

And now what is this Ignorance (adarrfana), this absence of knowledge ? Is it a function of the qualities ? Or, is it the non-reproduction of the mind which after having shown all the objects to the Puru^a has

become latent? That there should be absence of knowledge notwithstanding the presence of the knowable or the thing owned, is also unreasonable. Is it again the purposefulness of the qualities? Or, is it Nescience which has passed into the state of latency with its own appropriate mental state, and has become the seed which produces the mind appropriate to its own manifestation ? Is it again the manifestation of the potency of motion, on the potency of rest having expended itself. It has been said on this subject, that the Pradh&na, the material cause of all manifestation, would become what it is not, if it tended only to rest, because in that case there would not be any manifestation into phenomena ; nor would it be what it is, if it were to remain in constant motion, because in that case, the phenomena would become eternal and never disappear. It is only when it tends to both these states, that it can be called the Pradhana i (the cause of manifestation) not otherwise. The same considerations apply to any other causes that might be imagined. 1

Some say that Ignorance (adarrfann) is nothing but the power which manifests as knowing (dar^ana). As the text says, ‘ The activity of the Pradhana is for the sake of showing herself.’

Others say that Ignorance (adarsana) is the characteristic of both the knower (Purusa) and the knowable, because the Purusa possesses only the power of knowing all that may be known, but does not know, before the setting in of manifestation ; and the knowable possesses only the capacity of causing all effects, but is not known at the time. Here this knowledge, though of the very nature of the knowable, stands in need of the incoming of the Purusa for its achievement, and is therefore a characteristic of the knowable. Again although it is not of the nature of the Purusa, yet depending as it does for its completion upon the illumination of the knowable, Ignorance looks as if it were a characteristic of the Puru§a.

Some again say that Ignorance is seeing or knowing (darrfana) only.

These are alternative conceptions of the teaching only. This manifoldness of alternative conceptions is the common ground for the conjunction of the qualities with all the Purus<as.