"Those who are attached to the impersonal Brahman or the localized Supersoul are also partially Krsna conscious, because impersonal Brahman is the spiritual ray of Krsna and Supersoul is the all-pervading partial expansion of Krsna. Thus the impersonalist and the meditator are also indirectly Krsna conscious. A directly Krsna conscious person is the topmost transcendentalist because such a devotee knows what is meant by Brahman or Paramatma. His knowledge of the Absolute Truth is perfect, whereas the impersonalist and the meditative yogi are imperfectly Krsna conscious."

Bhagavad-gita 6:10 Purport

Lord Sri Krsna, the Absolute Truth, is an eternally existent, cognizant, sentient being who is the ultimate cause of all causes. The Supreme Truth in His cognizant energy feature, known as Brahman, is present throughout the entire cosmic existence. As our own consciousness pervades our body, the consciousness of the Absolute is similarly manifest through His Brahman feature. Some yogis seek to merge with the formless Brahman effulgence of the Lord, which is the invisible, inferior feature. While the concept of impersonal Brahman is spiritual, this Yogi has not attained the highest spiritual understanding of the Personality of Godhead, because impersonal Brahman is subordinate to the complete Absolute. In the Brahma-sutra, Brahman is explained to be like the rays of the sunshine. The impersonal Brahman is the shining rays of the Supreme Personality of Godhead, who is like the sun. Impersonal Brahman is incomplete realization of the absolute whole.

The Supreme Truth is also eternally manifest in the sub-atomic form called Paramatma. In this feature, the Absolute Truth manifests as four-handed, fully-bedecked persons, each known as Paramatma. These sub-atomic persons exist in the spaces between atoms and also within each atom. In His Paramatma feature, the Lord permeates the entire cosmos. These Paramatmas, while uncountably multiplied, are actually one single entity through which the Absolute Truth remains fully cognizant of every subatomic point of subspace throughout all creation. While Paramatma is also partial realization of the Supreme Absolute, a Krsna conscious yogi is the perfect seer because he sees Krsna, the Supreme, situated in everyone's heart as Supersoul (Paramatma).

The same Supreme Truth remains manifest at all times under all circumstances in His eternal personal form known as Bhagavan, who is the Supreme Personality of Godhead. The Sanskrit word bhagavan is explained in Bhagavad-gita as the Supreme Personality who possesses all riches, all strength, all fame, all beauty, all knowledge and all renunciation. There are many persons who are very rich, very powerful, very beautiful, very famous, very learned, and very much detached, but no one can claim that he possesses all riches, all strength, etc., entirely. Only Krsna can claim this because He is the Supreme Personality of Godhead. No living entity, including Brahma, Lord Siva, or Narayana, can possess opulences as fully as Krsna. Therefore it is concluded in the Brahma-samhita by Lord Brahma himself that Lord Krsna is the Supreme Personality of Godhead. The yogi who has achieved realization of Bhagavan, the Supreme Personality, has attained the topmost level of transcendental knowledge.

Bhaktivedanta Book Trust. Excerpted from text and purport of HDG A.C. Bhaktivedanta Swami Srila Prabhupada.