Like most Hindus, I often find myself perplexed when called upon to explain to others what Hinduism is. I find that the major difficulty a modern Hindu faces in defining Hinduism to others stems from his difficulty in defining it to himself. This is especially the case with the "educated Hindu" who has unconsciously acquired the habit of looking at himself and his civilization through Christian eyes. As a result, his reaction is invariably defensive, and he mumbles something like "essential truth in all religions," or sarva dharma samatva, or some such equally meaningless platitude. But this habit-of measuring something with alien values-is a very serious limitation if anyone wants to understand what Hinduism is about.

The problem runs deep. The vision and vocabulary of a revealed religion like Christianity and Islam are fundamentally unsuited to describing Hinduism, for Hinduism is an evolved and not a revealed religion. The problem is not just lack of sympathy, it is the severe limitation of the concept of religion as the revelations of a book or a prophet. Trying to understand Hinduism in terms of a revealed belief system or creed is like trying to understand quantum mechanics through Newton's laws of motion. It just cannot be done. One must try to understand Hinduism on its own terms, not in terms of the internal and external features borrowed from other creeds.

I approach this task as a scientist and not as a theologian or a "true believer." Though born into a Hindu family, I am not by any means a devout Hindu. I am only an example of the freedom of choice that Hinduism grants me in matters of ritual and practice. My interest in Hinduism stems from my work in history and philosophy of science. I discovered that the concept of mathematical proof can be traced to yogic principles described in the famous Yogasutra written by the legendary Sage Patanjali. This greatly intrigued me. The most rational of the rational sciences has religious and mystical roots! It will no doubt come as a surprise to many readers to learn that "rational thinking," something we all prize so highly, has mystical roots. Both Patanjali and the Greek Pythagoras were mystics, and yet they laid the foundation for the rational processes on which our own civilization depends. This is what made me look deeper into the religious thought of the Hindus and the Greeks.

Briefly, here are the five basic features of Hindusim I found in my research: 1) It has no historical beginning. The Rig Veda, the oldest of the Hindu scriptures, is stated to be eternal and to have always existed. Speaking as a scientist, I find this claim hard to accept. But there is no period in time which we can definitely point to and say, "This is when the Rig Veda began to be composed." Unlike Christianity and Islam, which are historical religions, we cannot find a specific date or even a century or millennium when Hinduism began. 2) It is not a revealed religion. It has no single authority or book. "Veda" simply means "knowledge that was discerned by the Vedic seers." It is not a theology or a belief system that everyone is required to acknowledge. A Hindu is free to question any or all of the scriptures. He does not cease being a Hindu for doing so. Hindu scripture is meant to be a guide. 3) Hinduism recognizes no prophet as having exclusive claim over religious truth. This is undoubtedly the greatest difference between Hinduism and revealed religions. A Hindu who believes in the existence of God (or Gods) is not required to acknowledge an intermediary as a prophet or as the chosen agent of God. Every Hindu man, woman and child has the same direct access to God through his or her own efforts. 4) Hinduism does not recognize claims of exclusivity or a clergy. Exclusivity divides the world into believers and nonbelievers, which Hinduism does not. As a result, Hinduism has no clergy to monitor and enforce belief. 5) The only "dogma" of Hinduism is freedom of choice and conscience. Hindu religious literature is concerned mainly with the knowledge and method necessary to learn the truth about God. Any accommodation of a belief system that denies one's freedom of choice and conscience is fundamentally incompatible with Hinduism. It is our duty to defend this precious freedom and preserve and pass it on to future generations.

Navaratna Rajaram is the Vice President of the International Institute of Indian Studies in Ottawa, Canada. He is a mathematician, computer scientist, linguist and a researcher in artificial intelligence and robotics.