Most confidential knowledge - can be understood only by association with pure devotees

By devotional service or by the most confidential knowledge, one can understand very easily how the different energies of the Lord are working. One part of energy is manifesting the material world; the other (superior) part of His energy is manifesting the spiritual world. And the via medium energy is manifesting the living entities who are serving either of the above mentioned energies. 

The living entities serving material energy are struggling hard for existence and happiness, which is presented to them as illusion. But those in the spiritual energy are placed under the direct service of the Lord in eternal life, complete knowledge and perpetual bliss. The Lord desires, as He has directly said in the Bhagavad-gita, that all conditioned souls, rotting in the kingdom of material energy, come back to Him by giving up all engagements in the material world. This is the most confidential part of knowledge. 

But this can be understood only by the pure devotees, and only such devotees enter the kingdom of God to see Him personally and serve Him personally. SB 1.5.31