When I first came in contact with Srila Prabhupada’s Bhagavad-gita As It Is, I was excited about my discovery. I’d been searching for answers to life’s great questions, and after only a short time in the company of the philosophy of the Gita, I had to concur with Henry David Thoreau, who called it “stupendous” and said that compared to the Gita, “our modern world and its literature seem puny and trivial.”

When I shared my enthusiasm for the Bhagavad-gita with my coworkers, a young woman in the office expressed skepticism. So I asked her a question meant to capture in a simple way what the Gita teaches.

“How do you know what’s right and what’s wrong?” I asked her.
“My mother tells me.”
“How does she know?”
“I don’t know – she just does.”
While I appreciated her respect for her mother, her answer struck me as, well, trivial.

Seeing a devotee’s conviction about Krishna consciousness, people may ask, “But how do you know it’s true?”

The answer can be summed up in three words: sadhu, sastra, and guru. These three authorities – saintly persons, Vedic scriptures, and the spiritual master – tell us what most mothers (and everyone else) can’t tell us about the nature of reality and how to live in harmony with it.

Srila Prabhupada compared sadhu-sastraguru to three parallel tracks that carry us forward to the supreme destination: Lord Krishna in the spiritual world. The primary authority is sastra. In the Bhagavad-gita (16.23) Krishna says, “He who discards scriptural injunctions and acts according to his own whims attains neither perfection, nor happiness, nor the supreme destination.” The spiritual authority of the sadhu and the guru derives from their living according to the injunctions of sastra and citing sastra as the unerring authority.

Furthermore, the sastra includes the realizations of sadhus. For example, in the Srimad- Bhagavatam we hear not only from incarnations of God, but also from many self-realized souls fully dedicated to God. Twelve primary sadhus, beginning with Lord Brahma, the first created being in the universe, are known as the mahajanas, or “great persons.” The Mahabharata tells us we should avoid the opinions of speculative philosophers and follow the path of the mahajanas, in whose hearts are hidden the truth of religious principles. They unanimously champion devotional service to Krishna as the supreme occupation for humanity.

The sadhu and guru validate sastra. Srila Prabhupada and the previous acaryas (sadhus) in his line accept the Vedic scriptures as sources of perfect knowledge, as do many other spiritual lineages tracing back into the remote past.

If the authority of sadhu-sastra-guru seems like an endless self-validating circle, understand it instead as a system of checks and balances. We see the same dynamic operating in modern life. If we want to know whether a certain book is a valid law book, we ask a lawyer. The same principle applies to medicine, engineering, education, and many other fields. And the books in various fields help us understand the qualifications of the practitioners of those professions.

I have no doubt that my initial encounter with the Bhagavad-gita would have been less profound – and possibly fruitless – had the introduction been made by someone other than Srila Prabhupada. I’d even say that although sastra is the fundamental authority, my faith in Krishna consciousness rests primarily on my faith in Prabhupada. I know Krishna consciousness is reality because I know Srila Prabhupada, through his teachings and example. His integrity is unimpeachable, his depth of spiritual realization clearly evident. So, when Prabhupada speaks about the highest truth, I feel compelled to believe him.