Caitanya Mahāprabhu says, āmāra ājñāya guru hañā (CC Madhya 7.128): "You just become guru on My order." You cannot become guru automatically, without following the order of jagad-guru. The government servant . . . who is government servant? Who is strictly following the government order, that is government servant. Anyone can say: "I am government servant." No. How you can be? Similarly, guru means who is following the principles given by the jagad-guru. The . . . he's guru.
So the principle . . . what is that principle? Sarva-dharmān parityajya mām ekaṁ śaraṇaṁ vraja (BG 18.66). This is principle. "You give up all these nonsense activities. Simply surrender." So one who has surrendered to Kṛṣṇa fully, no other business, he is guru. This is the definition of guru. There is no difficult to understand who is guru. One who follows strictly the principles laid down by jagad-guru, he is guru. So the jagad-guru says . . . because we have to learn everything, especially spiritual subject matter, from guru. Tad-vijñānārthaṁ sa gurum eva abhigacchet (MU 1.2.12). This is the injunction of the Vedas. If you want to understand Brahman, athāto brahma jijñāsā . . . this life, human life, is meant for inquiring about the Absolute Truth: athāto brahma jijñāsā. This is not meant for any other purpose. This life, any life, there is no question of inquiring about "Where shall I eat? Where shall I sleep? Where shall I have sex? How shall I be saved from fear?" There is no such question. This is already arranged.