The Guru who does not reveal the Path to Truth is not a Sat Guru. He may be a guru relating to a concept of wisdom, a branch of wisdom. There can be gurus who promote concepts and thereby gradually control and possess people. The false gurus exist as much as the Sat Gurus. The existence of false gurus is clear proof of the existence of Sat Gurus. How can there be a counterfeit unless there is the original?
According to the sincerity of purpose and the degree of purity, one is attracted to a Sat Guru or a false guru. "Birds of a feather flock together" is a popular saying. Beings of the same quality group, gather, under a big manifestation of that quality. If one is looking for Truth sincerely and has a fairly pure life, it is likely that the intensity of sincerity would lead him to a Sat Guru.
Prahlada (the foremost of the world disciples mentioned in Srimad Bhagavata) says as under:
Those who are not Sat Gurus conceive and contrive ways and means to enslave the followers and fulfil their individual agenda. They do not pave the way for the followers towards the Law, the Truth, and the bliss of self-realisation. They are to be discarded at once. The Sat Guru leads his followers towards the Truth, the "all permeating consciousness" who presides over the creation, having created it. He would lead his chelas towards immortality and eternity. He would lift them up from the wheel of birth and death.
Men with common sense, introspect, before they plunge into any action. It should be so even in relation to the Path to the subtle/supermundane world. Sat Guru creates the taste towards the Truth. Through his teachings, he inspires the pupils to follow the Law. He also encourages self-study, self-analysis, self-introspection and inaugurates the will for self- transformation. He gives the contemplative and meditational techniques to enable the pupil to dip into the super-conscious layers of him from the superficial layers of his mind. He does not encourage people to gather around him all the time. He would also not encourage them to publicise him and proclaim him as the great one. He remains simple and teaches simplicity to the followers, for Truth is simple. Aggrandisement of ones personality is foreign to the quality of the Sat Guru.
A guru that aggrandises himself gathers around him people of similar quality who aggrandise themselves in association with him. Just as the guru tries to accomplish his individual agenda, so the followers too, try to accomplish and fulfil their individual objectives. Thus, the community around the one who is not a Sat Guru would be like a social club, people fulfilling their individual tasks through social contacts and related influence. Such false teachers cast a shadow on the true teachers, which is not seen as a sin by a Sat Guru, but as a protection. The light feels secure when hidden from the profane. The Sat Guru knows that all that popular activity around him is like the foam around the water, which does not last long. He therefore does not allow excessive foam and fog to gather around him. In the Age of Kali there are many who proclaim themselves as gurus and distort the most sacred tradition of Teacher-student. A Sat Guru is known by the path he emphasises, by the simplicity he demonstrates and the transformation that happens to the people around him.
Excerpt from "Sri Dattatreya. The Symbol & the Significance"
by Dr. K. Parvathi Kumar