In Bhagavad-gītā (BG 15.7) Lord Kṛṣṇa clearly says, mamaivāṁśo jīva-loke jīva-bhūtaḥ: "All the living entities are part of Me." Therefore the living entities are qualitatively the same as the Supreme Personality of Godhead, who is the leader, the Supreme among all the living entities. In the Vedas it is said, nityo nityānāṁ cetanaś cetanānām (Kaṭha Upaniṣad 2.2.13): the Lord is the chief individual living entity, the leader of the subordinate living entities. Because the living entities are parts or samples of God, their qualities are not different from those of the Supreme Lord. The living entities have the same qualities as the Lord, just as a drop of sea water is composed of the same chemicals as the great sea itself. Thus there is oneness in quality but a difference in quantity. One can understand the Supreme Personality of Godhead by understanding the sample, the living entity, because all the qualities of God exist in a minute quantity in the living entities. There is oneness, but God is great whereas the living entities are extremely small. Aṇor aṇīyān mahato mahīyān (Kaṭha Upaniṣad 1.2.20). The living entities are smaller than the atom, but God is greater than the greatest. Our conception of greatness may be represented by the sky because we think of the sky as being unlimitedly big, but God is bigger than the sky. Similarly, we have knowledge that the living entities are smaller than atoms, being one ten-thousandth the size of the tip of a hair, yet the quality of being the supreme cause of all causes exists in the living entity as well as in the Supreme Personality of Godhead. Indeed, it is due to the presence of the living entity that the body exists and bodily changes take place. Similarly, it is because the Supreme Lord is within this universe that the changes dictated by the material laws occur.
The word ekaḥ, meaning "individual," is significant. As explained in Bhagavad-gītā (BG 9.4), mat-sthāni sarva-bhūtāni na cāhaṁ teṣv avasthitaḥ. Everything, material and spiritual, including earth, water, air, fire, sky and the living entities, exists on the platform of spirit soul. Although everything is an emanation from the Supreme Personality of Godhead, one should not think that the Supreme Lord is dependent upon anything else.
Both God and the living entity are fully conscious. As living entities, we are conscious of our bodily existence. Similarly, the Lord is conscious of the gigantic cosmic manifestation. This is confirmed in the Vedas. Yasmin dyauḥ pṛthivī cāntarīkṣam. Vijñātāram adhikena vijānīyāt. Ekam evādvitīyam. Ātma-jyotiḥ samrāḍ ihovāca. Sa imān lokān asṛjata. Satyaṁ jñānam anantam. Asaṅgo hy ayaṁ puruṣaḥ. pūrṇasya pūrṇam ādāya pūrṇam evāvaśiṣyate (Śrī Īśopaniṣad, Invocation). All these Vedic injunctions prove that both the Supreme Personality of Godhead and the minute soul are individual. One is great, and the other is small, but both of them are the cause of all causes—the corporally limited and the universally unlimited.
We should always remember that although we are equal to the Supreme Personality of Godhead in quality, we are never equal to Him in quantity. Persons with a small fund of intelligence, finding themselves equal in quality with God, foolishly think that they are equal in quantity also. Their intelligence is called aviśuddha-buddhayaḥ-unpolished or contaminated intelligence. When such persons, after endeavoring hard for many, many lives to understand the supreme cause, are finally in actual knowledge of Kṛṣṇa, Vāsudeva, they surrender unto Him (vāsudevaḥ sarvam iti sa mahātmā sudurlabhaḥ (BG 7.19)). Thus they become great mahātmās, perfect souls. If one is fortunate enough to understand his relationship with God, knowing that God is great (vibhu) whereas the living entity is small (aṇu), he is perfect in knowledge. The individual exists in darkness when he thinks that he is the material body and that everything in relationship with the material body belongs to him. This is called ahaṁ mama (janasya moho 'yam ahaṁ mameti (SB 5.5.8)). This is illusion. One must give up his illusory conception and thus become fully aware of everything.