Kṛṣṇa is the Supreme Person, but at the same time He is beyond the knowledge of Brahman and Paramātmā. The yogīs and jñānīs are confused in their attempts to understand Kṛṣṇa. Although the greatest of the impersonalists, Śrīpāda Śaṅkarācārya, has admitted in his Gītā commentary that Kṛṣṇa is the Supreme Personality of Godhead, his followers do not accept Kṛṣṇa as such, for it is very difficult to know Kṛṣṇa, even though one has transcendental realization of impersonal Brahman.
Kṛṣṇa is the Supreme Personality of Godhead, the cause of all causes, the primeval Lord Govinda. Īśvaraḥ paramaḥ kṛṣṇaḥ sac-cid-ānanda-vigrahaḥ/ anādir ādir govindaḥ sarva-kāraṇa-kāraṇam. It is very difficult for the nondevotees to know Him. Although nondevotees declare that the path of bhakti, or devotional service, is very easy, they cannot practice it. If the path of bhakti is so easy, as the nondevotee class of men proclaim, then why do they take up the difficult path? Actually the path of bhakti is not easy. The so-called path of bhakti practiced by unauthorized persons without knowledge of bhakti may be easy, but when it is practiced factually according to the rules and regulations, the speculative scholars and philosophers fall away from the path.
(Bhagavad-gita------7:3------purport).

There are many different kinds of living entities—human beings, demigods, animals, etc.—and each and every one of them is under the influence of material nature, and all of them have forgotten the transcendent Personality of Godhead. Those who are in the modes of passion and ignorance, and even those who are in the mode of goodness, cannot gobeyond the impersonal Brahman conception of the Absolute Truth. They are bewildered before the Supreme Lord in His personal feature, which possesses all beauty, opulence, knowledge, strength, fame and renunciation. When even those who are in goodness cannot understand, what hope is there for those in passion and ignorance? Kṛṣṇa consciousness is transcendental to all these three modes of material nature, and those who are truly established in Kṛṣṇa consciousness are actually liberated.
(Bhagavad-gita------7:13------purport).

Brahman is indestructible and eternally existing, and its constitution is not changed at any time. But beyond Brahman there is Parabrahman. Brahman refers to the living entity, and Parabrahman refers to the Supreme Personality of Godhead. The constitutional position of the living entity is different from the position he takes in the material world. In material consciousness his nature is to try to be the lord of matter, but in spiritual consciousness, Kṛṣṇa consciousness, his position is to serve the Supreme. When the living entity is in material consciousness, he has to take on various bodies in the material world. That is called karma, or varied creation by the force of material consciousness.
(Bhagavad-gita------8:3------purport).

There are many examples of this in Vedic literature. The four Kumāras were situated first in the impersonal Brahman conception of truth, but then they gradually rose to the platform of devotional service. One who cannot elevate himself beyond the impersonal conception of Brahman runs the risk of falling down. In Śrīmad-Bhāgavatam it is stated that although a person may rise to the stage of impersonal Brahman, without going further, with no information of the Supreme Person, his intelligence is not perfectly clear. Therefore, in spite of being raised to the Brahman platform, there is the chance of falling down if one is not engaged in the devotional service of the Lord.
(Bhagavad-gita------14:27------purport).

The destination of transcendence is to become the personal associate of the Personality of Godhead, who is known as adhokṣaja, He who is beyond the reach of the senses. The renouncers of the world, the sannyāsīs, give up all worldly connections, namely, family, wife, children, friends, home, wealth—everything—to attain the transcendental bliss of Brahman happiness. But adhokṣaja happiness is beyond Brahman happiness. The empiric philosophers enjoy a transcendental quality of bliss by philosophical speculation on the Supreme Truth, but beyond that pleasure is the pleasure enjoyed by Brahman in His eternal form of the Personality of Godhead. Brahman bliss is enjoyed by living entities after liberation from material bondage. But Parabrahman, the Personality of Godhead, enjoys eternally a bliss of His own potency, which is called the hlādinī potency.
(Srimad Bhagavatam------3:1:31------purport).

According to the Vedic version there is no existence beyond Brahman. Sarvaṁ khalv idaṁ brahma (Chāndogya Upaniṣad 3.14.1). It is stated also in the Viṣṇu Purāṇa that whatever we see is parasya brahmaṇaḥ śaktiḥ; everything is an expansion of the energy of the Supreme Absolute Truth, Brahman. When Brahman is mixed with the three qualities goodness, passion and ignorance, there results the material expansion, which is sometimes called saguṇa Brahman and which consists of these twenty-five elements. In the nirguṇa Brahman, where there is no material contamination, or in the spiritual world, the three modes—goodness, passion and ignorance—are not present. Where nirguṇa Brahman is found, simple unalloyed goodness prevails. Saguṇa Brahman is described by the Sāṅkhya system of philosophy as consisting of twenty-five elements, including the time factor (past, present and future).
(Srimad Bhagavatam------3:26:15------purport).

In the Upaniṣads is the statement yato vā imāni bhūtāni jāyante. Everything is generated from Lord Viṣṇu, everything is maintained by Him, and everything is annihilated by His energy. Therefore, by their actions and reactions, the energies which come from Him create the cosmic manifestations and also dissolve the whole creation. Thus the Lord is the cause and also the effect. Whatever effect we see is the interaction of His energy, and because the energy is generated from Him, He is both cause and effect. Simultaneously, everything is different and the same. It is said that everything is Brahman: sarvaṁ khalv idaṁ brahma. In the highest vision, nothing is beyond Brahman, and therefore Lord Brahmā and Lord Śiva are certainly nondifferent from Him.
(Srimad Bhagavatam------4:7:50------purport).

The Absolute Truth is realized first as impersonal Brahman, then as Paramātmā, and finally as Bhagavān. Thus the Personality of Godhead, Bhagavān, is parataḥ parāt, beyond Brahman and Paramātmā realization. In this connection, Śrīla Jīva Gosvāmī points out that parataḥ parāt means "better than the best." The best is the spiritual world, and it is known as Brahman. The Supreme Personality of Godhead, however, is known as Parabrahman. Therefore parataḥ parāt means "better than Brahman realization."
(Srimad Bhagavatam------4:30:31------purport).