jñānena tu tad ajñānam yeṣāṃ nāśitam ātmanaḥ | teṣām ādityavaj jñānaṃ prakāśayati tat param
“As the sun dispels darkness and illuminates everything, so divine knowledge destroys ignorance and reveals the transcendental Absolute Truth.” — Bhagavad-Gītā 5.16    

Śāstra, Guru, Sādhu

Vedic knowledge is not a matter of academic scholarship. The one who teaches this knowledge and the one who receives it must both be qualified. A blind teacher cannot describe the shape and colours of an object and a blind disciple cannot comprehend such descriptions from a sighted person. In the Manu-Saṃhitā, a treatise that teaches Vedic knowledge, it is said:

Holy knowledge came to a Brāhmana and said to him, “I am your treasure, keep me, do not hand me over to a despiser, an unworthy one, so I will become very strong. Give me, as the guardian of your treasure, to a pure, self-controlled, abstinent and attentive Brāhmana.”

As we can see, Vedic knowledge is anything but a matter of dry scholarship, a matter for mental speculation; it is sacred, it is God Himself, and both – the giver and the receiver of this knowledge – must be worthy, must be qualified to give and receive it respectively.

Purity, self-control, abstinence and attentiveness are mentioned in this statement of the Manu-Saṃhitā as qualifications of a student of Vedic knowledge. The teacher of knowledge (Guru) must possess the same qualifications. In addition, he must have understood the knowledge through practical application and he must be able to teach it according to time, place and circumstances.

Spiritual knowledge is called ātmā-jñāna, brahma-jñāna or simply jñāna, and realised knowledge is called vijñāna. The Supreme Personality of Godhead is the origin of all material and spiritual manifestations. The process of realising Him is jñāna. Vijñāna means to see the Supreme Lord behind all and in all things through the application of jñāna (jñānena tu tad ajñānam yeṣāṃ nāśitam ātmanah | teṣām āditya-vaj jñānaṃ prakāśayati tat param   – B-G. 5.16). This is what the Vedic scriptures are ultimately about.

Three authorities of knowledge are Śāstra, Guru and Sādhu. Śāstra are the scriptures in which knowledge is recorded (see: the Vedic scriptures). Gurus are authorised teachers who pass on knowledge to qualified disciples and Sādhus are all holy personalities who have realised the knowledge and live it practically.

A Guru whose statements do not conform to the statements of the śastra is a pseudo-Guru; Sādhus who act contrary to the instructions of the revealed scriptures are pseudo-Sādhus and scriptures that teach something different from the Vedic scriptures and from the teachings of genuine Gurus are not recognised as śastra.

Spiritual knowledge is handed down and taught by a guru to his disciples in a disciplic succession called Guru-parampara. Disciples who become Gurus teach their disciples and those of their disciples who become Gurus themselves teach their disciples and so on. This is the Parampara system.

The original Guru (Ādi-Guru) from whom all knowledge emanates is Kṛṣṇa. He instructed Brahmā as the first living being in the universe; Brahmā instructed the four Kumaras, Narada and other sages; Narada instructed Vyāsadeva, Prahlada Mahārāja and others; Vyāsadeva instructed Śukadeva, etc. This Guru-parampara has been intact from the beginning of creation to the present day. Eminent teachers of spiritual knowledge today are some disciples of Bhaktisiddhanta Sarasvati Goswami and some of their disciples. Śrīla A.C. Bhaktivedanta Swami Prabhupada occupies a special place in the Guru-parampara, as he was the first to teach spiritual knowledge outside India. In fact, he was empowered by his spiritual master to spread the knowledge throughout the world. In this way, one can receive the spiritual knowledge in the Guru-parampara system.

Not everyone who claims to be a Guru or is called such by his followers is actually entitled and competent to teach spiritual knowledge. Since people in the kali-yuga, the present age, possess little philosophical or spiritual intelligence – their intelligence is misguided and mainly concerned with sense enjoyment, with inventing and building technical devices of all kinds and with inventing sales strategies – and are ignorant of the Śāstra, many Pseudo-Gurus and Pseudo-Sādhus have been able to spread false teachings and create a false idea of Guru and Sādhu in society. A so-called Sādhu who smokes hashish all day and lives by begging and a so-called Guru who teaches his followers how to satisfy their senses even better are figures of jokes. Only an ignorant person will call such people Sādhu or Guru.