yad idam manasa vaca
nasvaram grhyamanam ca
My dear Uddhava, the material universe that you perceive through your mind, speech, eyes, ears and other senses is an illusory creation that one imagines to be real due to the influence of maya. In fact, you should know that all of the objects of the material senses are temporary.
The question may be raised that since we find good and bad qualities throughout the material world, how can Lord Krsna advise Uddhava to see everything equally? In this verse Krsna explains that material good and evil are a creation of the illusory energy, just as the objects of a dream are a mental creation.
As stated in Bhagavad-gita, vasudevah sarvam iti: Lord Krsna is actually everything because He is present within everything and everything is present within Him. Krsna is sarva-loka-mahesvaram, the Lord and proprietor of all worlds. To see anything separate from Krsna is illusion, and attraction to any kind of material illusion, either good or bad, is ultimately useless since it obliges the living entity to continue wandering in the cycle of birth and death.
Seeing, hearing, smelling, tasting and touching constitute the activities of the five knowledge-gathering senses. Similarly, the voice, the hands, the legs, the anus and the genitals constitute the five working senses. These ten senses are organized around the mind, which is the center of material activity. When the living entity desires to exploit matter, he is covered by the three modes of nature. Thus he concocts different philosophical, political and social explanations of reality but never understands the Absolute Truth, Lord Krsna, who is beyond the contaminated perception of the material senses. One who is entangled in the network of material designations, such as race, nationality, sectarian religion, political affiliation, etc., is absorbed in the experience of combining his body and other bodies with material sense objects, thinking these sense objects to be sources of happiness and satisfaction. Unfortunately, the entire material world, along with the senses that experience it, is a temporary creation that will be annihilated by the time potency of the Supreme Lord. Despite our foolish hopes and dreams, there is no actual happiness on the material platform. The real truth is not material, nor is it temporary. The real truth is called atma, or the eternal soul, and among all eternal souls one is supreme. He is called the Personality of Godhead, and in His original form He is known as Krsna. The knowledge-gathering process culminates in perception of the inconceivable, transcendental form of Krsna. One who is not perceiving Krsna in everything and everything in Krsna is undoubtedly on the platform of mental concoction. In this verse Lord Krsna warns Uddhava to remain clear of this illusory platform of existence.