The Sanskrit root “Gu” means darkness or ignorance. “Ru” denotes the remover of that darkness. Therefore one who removes darkness of our ignorance is a Guru. Only he who removes our ultimate darkness, known as Maya, and who inspires and guides us on to the path of God-realization is the true Guru. Students also refer to their school teacher or college lecturer as guru. The connotation of the word guru in this case is one who imparts temporal knowledge (Apara Vidya) and is thus accordingly offered respect.
A spiritual aspirant, no matter how brilliant, can never attain such knowledge by his own endeavor. This is stipulated in the Shrimad Bhagwatam in which Jadbharat reveals to king Rahugan:
“O Rahugan! One cannot attain knowledge of Atma and Paramatma by performing penance, sacrifices, renunciation, Vedic study or worshipping deities of water, fire or the sun. But when the dust from the feet of a satpurush (God-realized Guru) sprinkles on our heads, then we can surely attain this knowledge.”
In essence, one can only attain salvation by serving the satpurush. Treading the path to God-realization by one’s own efforts is likened by the Katha Upanishad as walking on a razor’s edge. Adi Shankaracharya echoes a similar injunction: “If a person, despite possessing: a handsome, disease-free body, fame, a mountain of wealth, and even if he has studied the Vedas and all other scriptures, and has himself composed many scriptures, but has not surrendered himself at the feet of a Guru, then he has achieved nothing, nothing, nothing, nothing.”
The Guru plays a vital role in boosting the aspirant frequently, when he loses track, becomes despondent or simply runs out of steam. The aspirant is thus better able to obey the Guru if he understands the Guru’s glory.