Through mental speculation, even the greatest philosopher cannot know the Supreme Lord, who is the Absolute Personality of Godhead. He can be known only by His devotees through His mercy. In the Brahma-saṁhitā (5.34) it is stated that even if a nondevotee philosopher travels through space at the speed of the wind or the mind for hundreds of millions of years, he will still find that the Absolute Truth is far, far away from him. The Brahma-saṁhitā (5.37) further describes that the Absolute Personality of Godhead has His transcendental abode, known as Goloka, where He remains and engages in His pastimes, yet by His inconceivable potencies He can simultaneously reach every part of His creative energy. In the Viṣṇu Purāṇa His potencies are compared to the heat and light that emanate from a fire. Although situated in one place, a fire can distribute its light and heat for some distance; similarly, the Absolute Personality of Godhead, although fixed in His transcendental abode, can diffuse His different energies everywhere.

Although His energies are innumerable, they can be divided into three principal categories: the internal potency, the marginal potency and the external potency. There are hundreds and millions of subheadings to each of these categories. The dominating demigods who are empowered to control and administer such natural phenomena as air, light and rain are all classified within the marginal potency of the Absolute Person. Lesser living beings, including humans, also belong to the Lord’s marginal potency. The material world is the creation of the Lord’s external potency. And the spiritual sky, where the kingdom of God is situated, is the manifestation of His internal potency.

Thus the different energies of the Lord are present everywhere. Although the Lord and His energies are nondifferent, one should not mistake these energies for the Supreme Truth. Nor should one wrongly consider that the Supreme Lord is distributed everywhere impersonally or that He loses His personal existence. Men are accustomed to reaching conclusions according to their capacity for understanding, but the Supreme Lord is not subject to our limited capacity for understanding. It is for this reason that the Upaniṣads warn us that no one can approach the Lord by his own limited potency.

In the Bhagavad-gītā (10.2) the Lord says that not even the great ṛṣis and suras can know Him. And what to speak of the asuras, for whom there is no question of understanding the ways of the Lord? This fourth mantra of Śrī Īśopaniṣad very clearly suggests that the Absolute Truth is ultimately the Absolute Person; otherwise there would have been no need to mention so many details in support of His personal features.

Although the individual parts and parcels of the Lord’s potencies have all the symptoms of the Lord Himself, they have limited spheres of activity and are therefore all limited. The parts and parcels are never equal to the whole; therefore they cannot appreciate the Lord’s full potency. Under the influence of material nature, foolish and ignorant living beings who are but parts and parcels of the Lord try to conjecture about the Lord’s transcendental position. Śrī Īśopaniṣad warns of the futility of trying to establish the identity of the Lord through mental speculation. One should try to learn of the Transcendence from the Lord Himself, the supreme source of the Vedas, for the Lord alone has full knowledge of the Transcendence.

Every part and parcel of the Complete Whole is endowed with some particular energy to act according to the Lord’s will. When the part-and-parcel living entity forgets his particular activities under the Lord’s will, he is considered to be in māyā,illusion. Thus from the very beginning Śrī Īśopaniṣad warns us to be very careful to play the part designated for us by the Lord. This does not mean that the individual soul has no initiative of his own. Because he is part and parcel of the Lord, he must partake of the initiative of the Lord as well. When a person properly utilizes his initiative, or active nature, with intelligence, understanding that everything is the Lord’s potency, he can revive his original consciousness, which was lost due to association with māyā, the external energy.

All power is obtained from the Lord; therefore each particular power must be utilized to execute the will of the Lord and not otherwise. The Lord can be known by one who has adopted such a submissive service attitude. Perfect knowledge means knowing the Lord in all His features, knowing His potencies and knowing how these potencies work by His will. These matters are described by the Lord in the Bhagavad-gītā, the essence of all the Upaniṣads.