Those who undergo severe austerities and penances not recommended in the scriptures, performing them out of pride and egoism, who are impelled by lust and attachment, who are foolish and who torture the material elements of the body as well as the Supersoul dwelling within, are to be known as demons.
(Bhagavad-Gita-----17:5-6-----translation).

Materialistic men can think, although very imperfectly, of the huge universal space, comprehending an innumerable number of planets as big as the sun. They can see only the circular sky overhead, without any information that this universe, as well as many other hundreds of thousands of universes, are each covered by sevenfold material coverings of water, fire, air, sky, ego, noumenon and material nature, just like a huge football, pumped and covered, floating on the water of the Causal Ocean, wherein the Lord is lying as Mahā-Viṣṇu.
(Srimad Bhagavatam-----2:1:25-----purport).

Our senses of perception and of action, that is to say, our five perceptive senses of (1) hearing, (2) touch, (3) sight, (4) taste and (5) smell, as well as our five senses of action, namely (1) hands, (2) legs, (3) speech, (4) evacuation organs and (5) reproductive organs, and also our three subtle senses, namely (1) mind, (2) intelligence and (3) ego(thirteen senses in all), are supplied to us by various arrangements of gross or subtle forms of natural energy.
(Srimad Bhagavatam-----2:2:35-----purport).

The conditioned soul may take a form birth after birth due to his conditional existence in matter, but the self-centered impersonalists, by their gross ignorance, accept the Lord as one of them because of self-centered egoism, even after so-called advancement of knowledge in the Vedānta.
(Srimad Bhagavatam-----2:5:24-----purport).

The mental speculator tries to conquer the influence of time by future speculations of becoming Vāsudeva or the Supreme Lord himself by means of culturing knowledge and conquering over ego. But the process is not perfect. The perfect process is to accept Lord Vāsudeva as the Supreme in everything, and the best perfection in culturing knowledge is to surrender unto Him because He is the source of everything.
(Srimad Bhagavatam-----2:9:3-----purport).

There are three different types of creation, called mahā-kalpa, vikalpa and kalpa. In the mahā-kalpa the Lord assumes the first puruṣa incarnation as Kāraṇodakaśāyī Viṣṇu with all the potencies of the mahat-tattva and the sixteen principles of creative matter and instruments. The creative instruments are eleven, the ingredients are five, and all of them are products of mahat, or materialistic ego. These creations by the Lord in His feature of Kāraṇodakaśāyī Viṣṇu are called mahā-kalpa.
(Srimad Bhagavatam-----2:10:46-----purport).

Egoism in the mode of passion produces two kinds of senses—the senses for acquiring knowledge and the senses of action. The senses of action depend on the vital energy, and the senses for acquiring knowledge depend on intelligence.
(Srimad Bhagavatam-----3:26:31-----translation).

It has been explained in the previous verses that mind is the product of ego in goodness and that the function of the mind is acceptance and rejection according to desire. But here intelligence is said to be the product of ego in passion. That is the distinction between mind and intelligence; mind is a product of egoism in goodness, and intelligence is a product of egoism in passion. The desire to accept something and reject something is a very important factor of the mind.
(Srimad Bhagavatam-----3:26:31----purport).

Desire has to be purified. In the beginning, this purification process has to be carried out by the order of the spiritual master, since the spiritual master knows how the disciple's desires can be transformed into Kṛṣṇa consciousness. As far as intelligence is concerned, it is clearly stated here that it is a product of egoism in passion. By practice one comes to the point of the mode of goodness, and by surrendering or fixing the mind upon the Supreme Personality of Godhead, one becomes a very great personality, or mahātmā. In Bhagavad-gītā it is clearly said, sa mahātmā sudurlabhaḥ: "Such a great soul is very rare."
(Srimad Bhagavatam-----3:26:31----purport).

In this verse it is clear that both kinds of senses, the senses for acquiring knowledge and the senses for action, are products of egoism in the mode of passion. And because the sense organs for activity and for acquiring knowledge require energy, the vital energy, or life energy, is also produced by egoism in the mode of passion. We can actually see, therefore, that those who are very passionate can improve in material acquisition very quickly.
(Srimad Bhagavatam-----3:26:31----purport).

An important word in this verse is mukta-liṅgaḥ. Mukta means "liberated," and liṅga means "the subtle body." When a man dies, he quits the gross body, but the subtle body of mind, intelligence and ego carries him to a new body.
(Srimad Bhagavatam-----4:12:18----purport).

The mental condition of a baby is different from that of a boy, the mental condition of a boy is different from that of a young man, and the mental condition of a young man is different from that of an old man. So at death the process of changing bodies takes place due to the subtle body; the mind, intelligence and ego carry the soul from one gross body to another. This is called transmigration of the soul. But there is another stage, when one becomes liberated even from the subtle body; at that time the living entity is competent and fully prepared to be transferred to the transcendental or spiritual world.
(Srimad Bhagavatam-----4:12:18----purport).

No material planet, even Satyaloka, is comparable in quality to the spiritual planets, where the five inherent qualities of the material world—namely ignorance, misery, egoism, anger and envy—are completely absent.
(Sri Caitanya Caritamrta-----1:5:22-----purport).

A part of ego is the sky, a part of which is air, a part of which is fire, a part of which is water, a part of which is earth. Thus one universe inflates to an area of four billion miles in diameter. A yogī who desires gradual liberation must penetrate all the different coverings of the universe, including the subtle coverings of the three qualitative modes of material nature. One who does this never has to return to this mortal world.
(Sri Caitanya Caritamrta-----1:5:22-----purport).

Śaṅkarācārya says (sūtra 43) that devotees think that Pradyumna, who is considered to represent the senses, has sprung from Saṅkarṣaṇa, who is considered to represent the living entities. But we cannot actually experience that a person can produce senses. Devotees also say that from Pradyumna has sprung Aniruddha, who is considered to represent the ego. But Śaṅkarācārya says that unless the devotees can show how ego and the means of knowledge can generate from a person, such an explanation of the Vedānta-sūtra cannot be accepted, for no other philosophers accept the sūtras in that way.
(Sri Caitanya Caritamrta-----1:5:41-----purport).

Saṅkarṣaṇa, the second expansion, is Vāsudeva's personal expansion for pastimes, and since He is the reservoir of all living entities, He is sometimes called jīva. The beauty of Saṅkarṣaṇa is greater than that of innumerable full moons radiating light beams. He is worshipable as the principle of ego. He has invested Anantadeva with all the potencies of sustenance.
(Sri Caitanya Caritamrta-----1:5:41-----purport).

The Mokṣa-dharma Vedic scripture indicates that Pradyumna is the Deity of the total mind, whereas Aniruddha is the Deity of the total ego, but previous statements regarding the quadruple forms are confirmed in the Pañcarātra tantras in all respects.
(Sri Caitanya Caritamrta-----1:5:41-----purport).

The Pañcarātras state that the personality of jīva called Saṅkarṣaṇa has emerged from Vāsudeva, the supreme cause of all causes, that Pradyumna, the mind, has come from Saṅkarṣaṇa, and that Aniruddha, the ego, has come from Pradyumna. But one cannot say that the living entity (jīva) takes birth or is created, for such a statement is against the injunction of the Vedas.
(Sri Caitanya Caritamrta-----1:5:41-----purport).

As stated in the Kaṭha Upaniṣad (2.18), living entities, as individual spiritual souls, can have neither birth nor death. All Vedic literature declares that the living entities are eternal. Therefore when it is said that Saṅkarṣaṇa is jīva, this indicates that He is the predominating Deity of the living entities. Similarly, Pradyumna is the predominating Deity of the mind, and Aniruddha is the predominating Deity of the ego.
(Sri Caitanya Caritamrta-----1:5:41-----purport).

Since Saṅkarṣaṇa, Pradyumna and Aniruddha are, respectively, the predominating Deities of all living entities, the total mind and the total ego, the designation of Saṅkarṣaṇa, Pradyumna and Aniruddha as "jīva," "mind" and "ego" are never contradictory to the statements of the scriptures. These terms identify these Deities, just as the terms "sky" and "light" sometimes identify the Absolute Brahman.
(Sri Caitanya Caritamrta-----1:5:41-----purport).

Thus, in the Bhagavad-gītā and in all other Vedic literatures the superior energy (antimaterial principle) is accepted as the vital force, or the living spirit. This is also called the jīva. This living principle cannot be generated by any combination of material elements. There are eight material principles which are described as inferior energies, and they are: (1) earth, (2) water, (3) fire, (4) air, (5) ether, (6) mind, (7) intelligence and (8) ego. Apart from these is the living force, or the antimaterial principle, which is described as the superior energy. These are called "energies" because they are wielded and controlled by the supreme living being, the Personality of Godhead (Kṛṣṇa).
(Easy journey to other Planets).

The three types of egotism (ahaṅkāra) are technically known as vaikārika, taijasa and tāmasa. The mahat-tattva is situated within the heart, or citta, and the predominating Deity of the mahat-tattva is Lord Vāsudeva (S.B.3:26:21). The mahat-tattva is transformed into three divisions: (1) vaikārika, egotism in goodness (sāttvika-ahaṅkāra), from which is manifested the eleventh sense organ, the mind, whose predominating Deity is Aniruddha (SB 3.26.27–28); (2) taijasa, or egotism in passion (rājasa-ahaṅkāra), from which are manifested the active and knowledge-acquiring senses, along with the intelligence, whose predominating Deity is Lord Pradyumna (SB 3.26.29–31); and (3) tāmasa, or egotism in ignorance, from which sound vibration (śabda-tanmātra) expands. From sound vibration, the sky (ākāśa) is manifested, and then the senses, beginning with the sense of hearing, are also manifested (S.B.3:26:32). Of these three types of egotism, Lord Saṅkarṣaṇa is the predominating Deity. In the philosophical discourse known as the Sāṅkhya-kārikā, it is stated, sāttvika ekādaśakaḥ pravartate vaikṛtād ahaṅkārāt—bhūtādes tan-mātraṁ tāmasa-taijasādy-ubhayam.
(Sri Caitanya Caritamrta-----2:20:276-----purport).

It is confirmed in Śrīmad-Bhāgavatam (1.3.1) that when the Supreme Personality of Godhead descends as the first puruṣa incarnation of the material creation, He immediately manifests sixteen elementary energies. Known as the Mahā-Viṣṇu, He lies within the Causal Ocean, and it is He who is the original incarnation in the material world. He is the Lord of time, nature, cause and effect, mind, ego, the five elements, the three modes of nature, the senses and the universal form. Although He is master of all objects movable and immovable in the material world, He is totally independent.
(Teachings of Lord Caitanya).