The spirit soul, part and parcel of the Supreme Personality of Godhead, Sri Krishna is an eternal servant of Krishna. How he comes to the material world is very clearly explained as follows:

ajnanenavrtam jnanam
tena muhyanti jantavah

"Embodied beings, however, are bewildered because of the ignorance which covers their real knowledge." - Bhagavad-gita 5.15

A living entity is, by superior nature, full of knowledge. Nevertheless, he is prone to be influenced by ignorance due to his limited power. The Lord is omnipotent, but the living entity is not. The Lord is vibhu, or omniscient, but the living entity is anu, atomic. Because he is a living soul, he has the capacity to desire by his free will.

Although he is constitutionally eternal, blissful and cognizant, due to the littleness of his existence he forgets his constitutional position of service to the Lord, and is thus entrapped by nescience.

bhayam dvitiyabhinivesatah syad
isad apetasya viparyayo 'smrtih
tan mayayato budha abhajet tam
bhaktyaikayesam guru devatatma

Fear arises when a living entity misidentifies himself as the material body because of absorption in the external, illusory energy of the Lord. When the living entity thus turns away from the Supreme Lord, he also forgets his own constitutional position as a servant of the Lord. This bewildering, fearful condition is effected by the potency of illusion, called maya. Therefore, an intelligent person should engage unflinchingly in the unalloyed devotional service of the Lord, under the guidance of a bonafide spiritual master, whom he should accept as his worshipable deity and as is very life and soul.

One may now ask why does he forget his constitutional position? The potency of the Lord that enlightens us in the Lord's service is called chit-sakti. Srila Bhaktisiddhanta Sarasvati Thakura comments that when the living entity develops a spirit of independence he is forced to come to the material world, where he enters into various types of petty and undesirable behaviour that create a fearful situation. The bahiranga sakti, the illusory potency of the Supreme Lord, covers all trace of the chit sakti and imposes one material body after another upon the living entity for his gross sinful enjoyment. As further punishment, the living entity who has given up his loving relationship with Krishna loses all power to perceive the eternal, blissful form of the Supreme Lord, who is his actual shelter.

The living entity originally was in the service of Krishna; when he revolted against that constitutional position he was given this material existence. We say that they have been conditioned from time immemorial because no one can trace out when the living entity, the part and parcel of the Supreme Lord, became rebellious against the supremacy of the Lord. It is a fact that there are two classes of men - those who are obedient to the laws of the Supreme Lord and those who are atheists or agnostics, who do not accept the existence of God and who want to create their own laws. They want to establish that everyone can create his own laws or his own religious path. Without tracing out the beginning of the existence of these two classes, we can take it for granted that some of the living entities revolted against the laws of the Lord. Such entities are called conditioned souls, for they are conditioned by the three modes of material nature. Therefore the words gunair vichitrah are used here.

Why would the living entities who are in the service of the eternal Lord revolt against Him? Since everything in that situation is very natural and constitutional, the cause of this also is the nature of the living entity:

esa nityo 'vyayah suksma
esa sarvasrayah svadrk
atmamaya-gunair visvam
atmanam srjate prabhuh

"The living entity is eternal and imperishable because he actually has no beginning and no end. He never takes birth or dies. He is the basic principle of all types of bodies, yet he does not belong to the bodily category. The living entity is so sublime that he is equal in quality to the Supreme Lord. Nonetheless, because he is extremely small, he is prone to be illusioned by the external energy, and thus he creates various bodies for himself according to his different desires."

In this verse the philosophy of acintya-bhedabheda - simultaneous oneness and difference - is described. The living entity is eternal (nitya) like the Supreme Personality of Godhead, but the difference is that the Supreme Lord is the greatest, no one being equal to or greater than Him, whereas the living entity is suksma, or extremely small. The shastra describes that the magnitude of the living entity is one ten-thousandth the size of the tip of a hair. The Supreme Lord is all-pervading (andantara-stha-paramanu-cayantara-stham). Relatively, if the living entity is accepted as the smallest, there should naturally be inquiry about the greatest. The greatest is the Supreme Personality of Godhead, and the smallest is the living entity.

Another peculiar characteristic of the jiva is that he becomes covered by maya. Atmamaya-gunaih: he is prone to being covered by the Supreme Lord's illusory energy. The living entity is responsible for his conditional life in the material world, and therefore he is described as prabhu ("the master"). If he likes he can come to this material world, and if he likes he can return home, back to Godhead.

This maya that covers the living entity's constitutional knowledge of servitor-hood is known as avidya:

vidyavidye mama tanu
viddhy uddhava saririnam
moksa-bandha-kari adye
mayaya me vinirmite

"O Uddhava, both knowledge and ignorance, being products of maya, are expansions of My potency. Both knowledge and ignorance are beginningless and perpetually award liberation and bondage to embodied living beings." - Srimad Bhagavatam 11.11.3

Srila Sridhara Svami notes in this regard that although the Lord has explained in the first verse of this chapter that the living entity is never actually in bondage, and therefore never actually liberated, one may apply the terms bondage and liberation if one remembers that the living entity is eternally a transcendental fragment of the Personality of Godhead. Further, one should not misinterpret the words mayaya me vinirmite to indicate that both material bondage and liberation are temporary states, being creations of the potency of the Lord. Therefore, the term adye, or "primeval and eternal," is used in this verse. The vidya and avidya potencies of the Lord are stated to be creations of maya because they carry out the functions of the Lord's potencies. The vidya potency engages the living entities in the Lord's pastimes, whereas the avidya potency engages the living entities in forgetting the Lord and merging into darkness. Actually, both knowledge and ignorance are eternal alternatives of the marginal potecy of the Lord, and in this sense it is not incorrect to state that the living entity is either eternally conditioned or eternally liberated. The term vinirmite, or "produced" in this case indicates that the Lord expands His own energy as knowledge and ignorance, which display the functions of the Lord's internal and external potencies. Such potential exhibitions may appear and disappear in different times, places and circumstances, but material bondage and spiritual freedom are eternal options of the marginal potency of the Lord.

yaya ksetra-jna-saktih sa
vestita nrpa sarva-ga
samsara-tapan akhilan
avapnoty atra santatan

"O King, the Ksetra-jna-sakti is the living entity. Although he has the facility to live in either the material or spiritual world, he suffers the threefold miseries of material existence because he is influenced by the avidya [nescience] potency, which covers his constitutional position." - Vishnu Purana 6.7.62

taya tirohitatvac ca
saktih ksetra-jna-samjnita
sarva-bhutesu bhu-pala
taratamyena vartate

"This living entity, covered by the influence of nescience, exists in different forms in the material condition. O King, he is thus proportionately freed from the influence of material energy, to greater or lesser degrees." - Vishnu Purana 6.7.63

apareyam itas tv anyam
prakrtim viddhi me param
jiva-bhutam maha-baho
yayedam dharyate jagat

"Besides this inferior nature, O mighty-armed Arjuna, there is a superior energy of Mine, which consists of all living entities who are struggling with material nature and are sustaining the universe." - Bhagavad-gita 7.5

krishna bhuli 'sei jiva anadi-bahirmukha
ataeva maya tare deya samsara-duhkha

"Forgetting Krishna, the living entity has been attracted by the external feature from time immemorial. Therefore the illusory energy [maya] gives all kinds of misery in his material existence." - Chaitanya-caritamrita, Madhya-lila 20.117

When the living entity forgets his constitutional position as an eternal servant of Krishna, he is immediately entrapped by the illusory, external energy. The living entity is originally part and parcel of Krishna and is therefore the superior energy of Krishna. He is endowed with inconceivable minute energy that works inconceivably within the body. However, the living entity, forgetting his position, is situated in material energy. The living entity is called the marginal energy because by nature he is spiritual but by forgetfulness he is situated in the material energy. Thus he has the power to live either in the material energy or in the spiritual energy, and for this reason he is called marginal energy. He is sometimes attracted by the external illusory energy when he stays in the marginal position, and this is the beginning of his material life. When he enters the material energy, he is subjected to the three fold time measurement - past, present and future. Past, present, future belong only to the material world; they do not exist in the spiritual world. The living entity is eternal, and he existed before the creation of this material world. Unfortunately he has forgotten his relationship with Krishna. The living entity's forgetfulness is described herein as anadi, which indicates that it has existed since time immemorial. One should understand that due to his desire to enjoy himself in competition with Krishna, the living entity comes into material existence.

kabu svarge uthaya, kabu narake dubbaya
dandya-jane raja yena nadite cubaya

"In the material condition, the living entity is sometimes raised to higher planetary systems and material prosperity and sometimes drowned in a hellish situation. His state is exactly like that of a criminal whom a king punishes by submerging him in water and then raising him again from the water." - Chaitanya-caritamrita, Madhya-lila 20.118

In the Vedas it is stated, asango 'yam purusah: the living entity is always free from the contamination of the material world. One who is not materially infected and who does not forget Krishna as his master is called nitya-mukta. In other words, one who is eternally liberated from material contamination is called nitya-mukta. From time immemorial the nitya-mukta living entity has always been a devotee of Krishna, and his only attempt has been to serve Krishna. Thus he never forgets his eternal servitor-ship to Krishna. Any living entity who forgets his eternal relationship with Krishna is under the sway of the material condition. Bereft of the Lord's transcendental loving service, he is subjected to the reactions of fruitive activity. When he is elevated to the higher planetary systems due to worldly pious activities, he considers himself well situated, but subjected to punishment, he thinks himself improperly situated. Thus material nature awards and punishes the living entity. When the living entity is materially opulent, material nature is rewarding him. When he is materially embarrassed, material nature is punishing him.

Thus, the living entity, due to his constitutional minute independence desires Lordship, due to his 'anu' atomic and infinitesimal nature gets covered by the avidya potency, and finds himself in the material existence.

When he is properly using his independence, he is in 'chit' sakti. On his revolting, he is under 'maya' sakti:

krishnera svabhavika tina-sakti-parinati
cic-chakti, jiva-sakti, ara maya-sakti

"Lord Krishna naturally has three energetic transformations, and these are known as the spiritual potency, the living entity potency and the illusory potency." - Chaitanya-caritamrita, Madhya-lila 20.111

visnu-saktih para prokta
ksetrajnakhya tatha para
avidya-karma-samjnanya
tritiya saktir isyate

"Originally, Krishna's energy is spiritual, and the energy known as the living entity is also spiritual. However, there is another energy, called illusion, which consists of fruitive activity. That is the Lord's third potency." - Vishnu Purana

yaya ksetra-jna-saktih sa
vestita nrpa sarva-ga
samsara-tapan akhilan
avapnoty atra santatan

"O King, the Ksetra-jna-sakti is the living entity. Although he has the facility to live in either the material or spiritual world, he suffers the threefold miseries of material existence because he is influenced by the avidya [nescience] potency, which covers his constitutional position." - Chaitanya-caritamrita, Madhya-lila 20.114

As far as Brahmajyoti is concerned, it is all pervasive. It is not only in the Sayujya. The whole spiritual existence is also accommodated by the brahmajyoti, as well as the material existence with all its universes; Lord Shiva confirms this in his prayer:

yatredam byajyate visvam
visvasminn avabhati yat
tat tvam brahma param jyotir
akasam iva vistrtam

"My dear Lord, the impersonal Brahman spreads everywhere, like the sunshine or the sky. And that impersonal Brahman, which spreads throughout the universe and in which the entire universe is manifested, is You." - Srimad Bhagavatam 4.24.60

In Vedic literature it is said that everything is Brahman and nothing else. The whole cosmic manifestation rests on the Brahman effulgence. The impersonalists, however, cannot understand how such a huge cosmic manifestation can rest on a person. Thus this inconceivable power of the Supreme Personality of Godhead is not understood by the impersonalists; therefore they are puzzled and always denying that the Absolute Truth is a person. This wrong impression is cleared by Lord Shiva himself, who says that the impersonal Brahman, which is spread all over the universe, is nothing but the Supreme Lord Himself. Here it is clearly said that the Lord is spread everywhere, just like the sunshine, by virtue of His Brahman feature. This example is very easy to understand. All the planetary systems are resting upon the sunshine, yet the sunshine and the source of sunshine are aloof from the planetary manifestations. Similarly, the sky or air is spread everywhere; air is within a pot, but it also touches filthy places and sanctified places alike. In any case, the sky is uncontaminated. The sunshine also touches filthy places and sanctified places, and both are actually produced by the sun, but in any case the sun is aloof from all filthy things. Similarly, the Lord exists everywhere. There are pious things and impious things, but in the sastras the pious things are described as the front of the Supreme Lord, whereas impious things are described as the back of the Supreme Personality of Godhead. In Bhagavad-gita (9.4) the Lord clearly says:

maya tatam idam sarvam
jagad avyakta-murtina
mat-sthani sava-bhutani
na caham tesv avasthitah

"By Me, in My unmanifested form, this entire universe is pervaded. All beings are in Me, but I am not in them."

This verse of Bhagavad-gita explains that the Lord is spread everywhere by virtue of His Brahman feature. Everything rests in Him, yet He is not there. The conclusion is that without bhakti-yoga, without rendering devotional service to the Lord, even an impersonalist cannot understand the brahma-tattva, the Brahman feature. In the Vedanta-sutra it is stated: athato brahma-jijnasa. This means that Brahman, Paramatma or Parabrahman should be understood. In Srimad-Bhagavatam also the Absolute Truth is described as the one without a second, but He is realized in three features - impersonal Brahman, localized Paramatma and the Supreme Personality of Godhead. The Supreme Personality of Godhead is the ultimate issue, and in this verse Lord Shiva confirms that ultimately the Absolute Truth is a person. He clearly says: tat tvam brahma param jyotir akasam iva vistrtam."

Here is a common example: a successful businessman may have many factories and offices, and everything rests on his order. If someone says that the entire business rests on such and such a person, it does not mean that the person is bearing all the factories and offices on his head. Rather, it is running without interruption. Similarly, it is the brain and energy of the Supreme Personality of Godhead that carry on the complete manifestation of the material and spiritual worlds. The philosophy of monism, explained here very clearly, adjusts itself to the fact that the supreme source of all energy is the Supreme Personality of Godhead, Krishna. This is described very clearly. It is also stated how the impersonal feature of Krishna can be understood:

raso 'ham apsu kaunteya
prabhasmi sasi-suryayoh
pranavah sarva-vedesu
sabdah khe paurusam nrsu

"O son of Kunti [Arjuna], I am the taste of water, the light of the sun and moon, the syllable om in the Vedic mantras; I am the sound in ether and the ability in man." (Bg. 7.8)

In this way Krishna can be understood as the mystic power in everything.

The final aspect that the living entity leaves before getting covered by the darkness of avidya, is the effulgence present in the spiritual existence. When the conditioned living entity clears his consciousness from the material darkness, that is the first aspect that covers the formful aspect of the Lord too: hiranmayena patrena satyasapihitam mukham.

There are some confused arguments, that brahmajyoti is just collection of living entities in their sat feature etc: Actually, brahmajyoti accommodates spiritual existence, material existence and the souls who have attained sayujya liberation. Brahman that is the source of everything as mentioned in the Vedanta sutras is not jiva is very clear from Lord Siva's prayer.

To consider jiva as brahman (brahman means collection of jivas with no chit etc., ) is only supported by Sankara bhasya. Brahman, Paramatma and Bhagavan are the three features of the Supreme Lord. It is as absurd as thinking that jiva is Paramatma or Bhagavan.

Brahman doesn't mean just Sayujya either; This understanding is generally of the opposite school of thought, spearheaded by Sankaracharya. There are three kinds of impersonal schools:

1) vivarta vadis
2) brahma parinama vadis
3) jivesvara vadis

Vivarta vadis argue that the Brahman gets covered by maya; brahma parinama vadis argue that Brahman underwent a transformation; jivesvara vadis argue that jiva is Brahman.

All the above schools think that Brahman means effulgence and there is no variety in Brahman: nirvisesa; and the buddhists think that Brahman is void:sunya.

utsarpayaams tu tam murdhni
kramenavesya nihsprhah
vayum vayau ksitau kayam
tejas tejasy ayuyujat

"In this way, Prthu Maharaja gradually raised his air of life up to the hole in his skull, whereupon he lost all desire for material existence. Gradually he merged his air of life with the totality of air, his body with the totality of earth, and the fire within his body with the totality of fire." - Srimad Bhagavatam 4.23.15

When a living entity gives up the material coverings, he remains a spirit soul. This spirit soul must enter into the spiritual sky to merge into the Brahman effulgence. Unfortunately, unless the living entity has information of the spiritual world and the Vaikunthas, there is a 99.9 percent chance of his falling down again into material existence. There is, however, a small chance of being promoted to a spiritual planet from the Brahman effulgence,of the brahmajyoti. This brahmajyoti is considered by impersonalists to be without variety, and the Buddhists consider it to be void. In either case, whether one accepts the spiritual sky as being without variety or void, there is none of the spiritual bliss which is enjoyed in the spiritual planets, the Vaikunthas or Krishnaloka. In the absence of varieties of enjoyment, the spirit soul gradually feels an attraction to enjoy a life of bliss, and not having any information of Krishnaloka or Vaikunthaloka, he naturally falls down to material activities in order to enjoy material varieties.

It is very important not to mix up the definitions of the different potencies of the Lord, if one is actually interested in returning to his constitutional position as the servant of the Lord. This is the greatness of Vaishnava darsans.

According to Srila Jiva Goswami the living entity may be designated as jiva-maya, whereas matter is called guna-maya. The living entity places his living potency (jiva-maya) in the grip of the mundane qualitative potency (guna-maya) and falsely dreams that he is part and parcel of the material world. Such an artificial mixture is called illusion or ignorance.

When all of the Lord's potencies are correctly perceived in their proper categories, the living entity is liberated from material bondage and returns to his blissful eternal residence in the spiritual sky.

In Vedanta when the word Brahman or brahmajyoti is used, it doesn't just mean Sayujya at all. When the impersonal philosophers take the meaning of Brahman as just brahmajyoti it is to write off the whole spiritual world as nirvisesa - no variety. This they do it in order to explain the soul as brahman. But brahman on whom the Vedanta Sutra recommends enquiry is not this brahman:

"The Supreme Lord is all-pervading (andantara-stha-paramanu-cayantara-stham). Relatively, if the living entity is accepted as the smallest, there should naturally be inquiry about the greatest."(SB 6.16.9)

As far as the Vaishnava authorities are concerned brahmajyoti is not even considered as liberation. Liberation is to return back to our constitutional position as servants of Krishna. Therefore Vaishnava philosophers do not accept sayujya mukti to be within the category of mukti. According to them, mukti means transferal to the loving service of the Lord from one's serving maya. Lord Chaitanya also says in this connection that the constitutional position of a living entity is to render service to the Lord. That is real mukti. When one is situatedin his original position, giving up artificial positions, he is called mukta, or liberated. In the Padma Purana this is also confirmed: mukti means engagement in the service of the Lord."

The word labdhvapavargyam is significant in this verse, because according to Jiva Goswami, apavargyam, or the path of liberation, does not refer to merging into the impersonal Brahman but to salokyadi-siddhi, which means attaining the very planet where the Supreme Personality of Godhead resides. There are five kinds of liberation, and one is called sayuja-mukti, or merging into the existence of the Supreme, or the impersonal Brahman effulgence. However, since there is a chance of one's falling down again into the material sky from the Brahman effulgence, Srila Jiva Goswami advises that in this human form of life, he is actually cheated if he does not make preparations to go back home, back to Godhead."

To argue that sayujya is the origin of the soul, will prove the material existence a progressive stage in evolution. This means bondage is above liberation! This argument will encourage one in pavarga: fruitive nature to enjoy in heaven etc.

Also [if the sayuja is the origin of the soul] 'returning back home, back to Godhead' may mean attaining Sayujya.

This is how karma and jnana invade the Vaishnava darsana and a sampradaya can lose sight of goal at least for some time. Sriman Mahaprabhu in his discussion with the tattva vadis pointed this out as what happened to the Madhva line, after Sri Madhvacharya.

To establish anything else other than the Lord Himself as the source or origin of spirit, thus is a clear impersonal tendency. Brahma jijnasa means to enquire into Absolute Truth, Personality of Godhead, who is realised in three features, this is vidya:

Such liberation can be achieved by vidya, or perfect knowledge, which is understood in three phases called Brahman, Paramatma and Bhagavan, as described in Srimad-Bhagavatam. The ultimate phase of vidya, or knowledge, is to understand the Supreme Personality of Godhead. In Bhagavad-gita such knowledge is called raja-vidya, or the king of all knowledge, and it awards the supreme liberation.

Not only thinking that the goal of life is sayujya is mayavada; To think that it is the beginning of soul is also mayavada. The result of indulgence is such discussion will result in avoiding devotional service of the Lord and doubting the non-difference of the Holy name and the Lord:

A living entity is eternally an individual soul, and if he wants to merge into the spiritual whole, he may accomplish the realization of the eternal and knowledgeable aspects of his original nature, but the blissful portion is not realized. By the grace of some devotee, such a transcendentalist, highly learned in the process of jnana-yoga, may come to the point of bhakti-yoga, or devotional service. At that time, long practice in impersonalism also becomes a source of trouble, because he cannot give up the idea. Therefore an embodied soul is always in difficulty with the unmanifest, both at the time of practice and at the time of realization is against the nature of his spiritual blissful self. One should not take up this process. For every individual living entity the process of Krishna consciousness, which entails full engagement in devotional service, is the best way. If one wants to ignore this devotional service, there is the danger of turning to atheism. Thus the process of centering attention on the unmanifested, the inconceivable, which is beyond the approach of the senses, as already expressed in this verse, should never be encouraged at any time, especially in this age. It is not advised by Lord Krishna.