Knowledge of the transcendental science of the Upanisads can free one from the entanglement of existence in the material world, and when thus liberated, one can be elevated to the spiritual kingdom of the SP of Godhead by advancement in spiritual life
What the Upaniṣads describe as the impersonal Brahman is but the effulgence of His body, and the Lord known as the Supersoul is but His localized plenary portion. Lord Caitanya is the Supreme Personality of Godhead, Kṛṣṇa Himself, full with six opulences. He is the Absolute Truth, and no other truth is greater than or equal to Him.
The compilers of the Upaniṣads speak very highly of the impersonal Brahman. The Upaniṣads, which are considered the most elevated portion of the Vedic literatures, are meant for persons who desire to get free from material association and who therefore approach a bona fide spiritual master for enlightenment. The prefix upa- indicates that one must receive knowledge about the Absolute Truth from a spiritual master. One who has faith in his spiritual master actually receives transcendental instruction, and as his attachment for material life slackens, he is able to advance on the spiritual path. Knowledge of the transcendental science of the Upaniṣads can free one from the entanglement of existence in the material world, and when thus liberated, one can be elevated to the spiritual kingdom of the Supreme Personality of Godhead by advancement in spiritual life.
The beginning of spiritual enlightenment is realization of impersonal Brahman. Such realization is effected by gradual negation of material variegatedness. Impersonal Brahman realization is the partial, distant experience of the Absolute Truth that one achieves through the rational approach. It is compared to one's seeing a hill from a distance and taking it to be a smoky cloud. A hill is not a smoky cloud, but it appears to be one from a distance because of our imperfect vision. In imperfect or smoky realization of the Absolute Truth, spiritual variegatedness is conspicuous by its absence. This experience is therefore called advaita-vāda, or realization of the oneness of the Absolute.
The impersonal glowing effulgence of Brahman consists only of the personal bodily rays of the Supreme Godhead, Śrī Kṛṣṇa. Since Śrī Gaurasundara, or Lord Śrī Caitanya Mahāprabhu, is identical with Śrī Kṛṣṇa Himself, the Brahman effulgence consists of the rays of His transcendental body.
Similarly, the Supersoul, which is called the Paramātmā, is a plenary representation of Caitanya Mahāprabhu. The antar-yāmī, the Supersoul in everyone's heart, is the controller of all living entities. This is confirmed in the Bhagavad-gītā (15.15), wherein Lord Kṛṣṇa says, sarvasya cāhaṁ hṛdi sanniviṣṭaḥ: “I am situated in everyone's heart.” The Bhagavad-gītā (5.29) also states, bhoktāraṁ yajña-tapasāṁ sarva-loka-maheśvaram, indicating that the Supreme Lord, acting in His expansion as the Supersoul, is the proprietor of everything. Similarly, the Brahma-saṁhitā (5.35) states, aṇḍāntara-stha-paramāṇu-cayāntara-stham. The Lord is present everywhere, within the heart of every living entity and within each and every atom as well. Thus by this Supersoul feature the Lord is all-pervading.
Furthermore, Lord Caitanya is also the master of all wealth, strength, fame, beauty, knowledge and renunciation because He is Śrī Kṛṣṇa Himself. He is described as pūrṇa, or complete. In the feature of Lord Caitanya, the Lord is an ideal renouncer, just as Śrī Rāma was an ideal king. Lord Caitanya accepted the order of sannyāsa and exemplified exceedingly wonderful principles in His own life. No one can compare to Him in the order of sannyāsa. Although in Kali-yuga acceptance of the sannyāsa order is generally forbidden, Lord Caitanya accepted it because He is complete in renunciation. Others cannot imitate Him but can only follow in His footsteps as far as possible. Those who are unfit for this order of life are strictly forbidden by the injunctions of the śāstras to accept it. Lord Caitanya, however, is complete in renunciation as well as all other opulences. He is therefore the highest principle of the Absolute Truth.
By an analytical study of the truth of Lord Caitanya, one will find that He is not different from the Supreme Personality of Godhead Kṛṣṇa; no one is greater than or even equal to Him. In the Bhagavad-gītā (7.7) Lord Kṛṣṇa says to Arjuna, mattaḥ parataraṁ nānyat kiñcid asti dhanañjaya: "O conqueror of wealth (Arjuna), there is no truth superior to Me." Thus it is here confirmed that there is no truth higher than Lord Śrī Kṛṣṇa Caitanya.
The impersonal Brahman is the goal of those who cultivate the study of books of transcendental knowledge, and the Supersoul is the goal of those who perform the yoga practices. One who knows the Supreme Personality of Godhead surpasses realization of both Brahman and Paramātmā because Bhagavān is the ultimate platform of absolute knowledge.
The Personality of Godhead is the complete form of sac-cid-ānanda (full life, knowledge and bliss). By realization of the sat portion of the Complete Whole (unlimited existence), one realizes the impersonal Brahman aspect of the Lord. By realization of the cit portion of the Complete Whole (unlimited knowledge), one can realize the localized aspect of the Lord, the Paramātmā. But neither of these partial realizations of the Complete Whole can help one realize ānanda, or complete bliss. Without such realization of ānanda, knowledge of the Absolute Truth is incomplete.
This verse of the Caitanya-caritāmṛta by Kṛṣṇadāsa Kavirāja Gosvāmī is confirmed by a parallel statement in the Tattva-sandarbha, by Śrīla Jīva Gosvāmī. In the Eighth Part of the Tattva-sandarbha it is said that the Absolute Truth is sometimes approached as impersonal Brahman, which, although spiritual, is only a partial representation of the Absolute Truth. Nārāyaṇa, the predominating Deity in Vaikuṇṭha, is to be known as an expansion of Śrī Kṛṣṇa, but Śrī Kṛṣṇa is the Supreme Absolute Truth, the object of the transcendental love of all living entities.