Acharya Prashant explains that the only valid criterion for a Guru is the tangible impact on a person's life, specifically the removal of sorrow, doubt, and confusion. He emphasizes that a Guru has a functional utility; if they do not bring peace and clarity, they should be discarded. He warns against false Gurus who speak against science, demand blind faith, claim to offer "new" spirituality outside of established scriptures like the Upanishads or the Bhagavad Gita, or focus on entertainment rather than breaking the disciple's mental patterns. He highlights that a true Guru destroys the ego, while a false one merely entertains. Furthermore, he asserts that spirituality requires honest labor and is not a matter of miracles. A true disciple is defined by a supreme desire for liberation and the courage to value truth above all worldly possessions and ego, even enduring the "merciless love" of a Guru that shatters their illusions.