Although someone may say that the Supreme Person is different from the cosmic manifestation, actually He is not. The Lord says, mayā tatam idaṁ sarvam: "In My impersonal feature I am spread throughout the world." Therefore, this world is not different from Him. The difference is a difference in names. For example, whether we speak of gold earrings, gold bangles or gold necklaces, ultimately they are all gold. In a similar way, all the different manifestations of matter and spirit are ultimately one in the Supreme Personality of Godhead. ekam evādvitīyaṁ brahma. This is the Vedic version (Chāndogya Upaniṣad 6.2.1). There is oneness because everything emanates from the Supreme Brahman.
(Srimad Bhagavatam-----8:12:8-----purport).

The word deva refers to God, the Supreme Personality of Godhead, who is the original source of all the demigods, who are also called devas. In Bhagavad-gītā (B.G.10:2) the Lord says, aham ādir hi devānām: "I am the source of all the devas." The Supreme Lord, Viṣṇu, the Original person, expands in different forms. Tad aikṣata bahu syām (Chāndogya Upaniṣad 6.2.3). He alone has expanded into many. Advaitam acyutam anādim ananta-rūpam (Bs. 5.33).
(Srimad Bhagavatam-----10:1:56-----purport).

Unless one approaches a spiritual master, one remains in ignorance. Ācāryavān puruṣo veda (Chāndogya Upaniṣad 6.14.2): one has full knowledge about life when one is ācāryavān, controlled by the ācārya.
(Srimad Bhagavatam-----10:10:10-----purport).

In the Chāndogya Upaniṣad there is the following mantra: aitad-ātmyam idaṁ sarvam. This mantra indicates without a doubt that the entire world is Brahman. The Absolute Truth has inconceivable energies, as confirmed in the Śvetāśvatara Upaniṣad (parāsya śaktir vividhaiva śrūyate (Cc. Madhya 13.65, purport)), and the entire cosmic manifestation is evidence of these different energies of the Supreme Lord. The Supreme Lord is a fact, and therefore whatever is created by the Supreme Lord is also factual. Everything is true and complete (pūrṇam), but the original pūrṇam, the complete Absolute Truth, always remains the same.
(Sri Caitanya Caritamrta-----1:7:121-----purport).

Śrīla Bhaktivinoda Ṭhākura comments that if one does not clearly understand the meaning of pariṇāma-vāda, or transformation of energy, one is sure to misunderstand the truth regarding this material cosmic manifestation and the living entities. In the Chāndogya Upaniṣad (6.8.4) it is said, san-mūlāḥ saumyemāḥ prajāḥ sad-āyatanāḥ sat-pratiṣṭhāḥ. The material world and the living entities are separate beings, and they are eternally true, not false.
(Sri Caitanya Caritamrta-----1:7:122-----purport).

The Māyāvādī philosophers consider many Vedic mantras to be the mahā-vākya, or principal Vedic mantra, such as tat tvam asi (Chāndogya Upaniṣad 6.8.7), idaṁ sarvaṁ yad ayam ātmā and brahmedaṁ sarvam (Bṛhad-āraṇyaka Upaniṣad 2.5.1), ātmaivedaṁ sarvam (Chāndogya Upaniṣad 7.25.2) and neha nānāsti kiñcana (Kaṭha Upaniṣad 2.1.11). That is a great mistake. Only oṁkāra is the mahā-vākya. All these other mantras that the Māyāvādīs accept as the mahā-vākya are only incidental. They cannot be taken as the mahā-vākya, or mahā-mantra. The mantra tat tvam asi indicates only a partial understanding of the Vedas, unlike oṁkāra, which represents the full understanding of the Vedas. Therefore the transcendental sound that includes all Vedic knowledge is oṁkāra (praṇava).
(Sri Caitanya Caritamrta-----1:7:128-----purport).

In the Chāndogya Upaniṣad (6.2.3), it is said, tad aikṣata bahu syāṁ prajāyeya. This statement confirms the fact that when the Supreme Personality of Godhead wishes to become many, the cosmic manifestation arises simply by His glancing over material energy. It may be noted that the Supreme Lord glanced over the material nature before the creation of this cosmic manifestation. Before the creation there were no material minds or material eyes; therefore the mind by which the Supreme Personality of Godhead desired to create is transcendental, and the eyes with which He glanced over material nature are also transcendental. Thus the Lord's mind, eyes and other senses are all transcendental.
(Sri Caitanya Caritamrta-----2:6:145-146-----purport).

In the Chāndogya Upaniṣad (5.2.3), it is said that when the Supreme Personality of Godhead desires to become many, He turns over material nature. As also confirmed in Aitareya Upaniṣad (1.1), sa aikṣata: "The Lord glanced at material nature." The cosmic manifestation did not exist before His glance; therefore His glance is not materially contaminated. His seeing power existed before the material creation; therefore His body is not material. His thinking, feeling and acting are all transcendental.
(Teachings of Lord Caitanya).

According to Muktika Upaniṣad, there are 108 Upaniṣads. Among these are: (1) Īśa, (2) Kena, (3) Kaṭha, (4) Praśna, (5) Muṇḍaka, (6) Māṇḍūkya, (7) Tittiri, (8) Aitareya, (9) Chāndogya, (10) Bṛhad-āraṇyaka, (11) Brahma, (12) Kaivalya, (13) Jāvāla, (14) Śvetāśva, (15) Hansa, (16) Arunih, (17) Garbha, (18) Narayana, etc. These 108 Upanisads contain all knowledge about the Absolute Truth. Sometimes people inquire abou the meaning of these 108 prayer beads, but because we think there are 108 Upanisads which contain full knowledge of the Absolute Truth, therefore 108 beads are accepted. Sometimes on the other hand, the Vaiṣṇava transcendentalists think that the 108 beads represent the 108 companions of Lord Kṛṣṇa in His rāsa dance, and therefore 108 beads are accepted.
(Teachings of Lord Caitanya).