An important Hindu principle is the concept of unity of all existence. This unity of all life is a central theme of Hinduism.
Ward J Fellows writes, ‘Oneness is not the one word to describe the essence of Hinduism, but it is as close as we can get to a one-word characterization.’ (Ward J Fellows, Religions East and West (New York: Holt, Rinehart & Winston, 1979), 71.) Hinduism holds that all things in this world are manifestations of the same ultimate Reality. The differences that we see around us are only phenomenal and do not impinge on that Reality. There is unity behind the diversity. Advaita philosophy teaches us the absolute oneness of all beings. Brahman (cosmic consciousness) and Atman (the soul) are identical. Accepting this Advaita doctrine, Gandhiji declares: ‘The chief value of Hinduism lies in holding the actual belief that all life (not only human beings, but all sentient beings) is one, i.e. all life is coming from the one universal source.’ (Raghavan Iyer, The Moral and Political Writings of Mahatma Gandhi (Oxford : Clarendon Press, 1986), 1.515.)
This acceptance of the unity of all life is the unique outlook of Hinduism. As all creatures are identical with the same ultimate Reality, a true Hindu has the responsibility to protect all living beings. By worshipping the cow, Hindus emphasize the need for protecting all living creatures. Again, cow protection shows that Hindus have a strong faith in ahimsa. Ahimsa is one of the important virtues; one of it earliest explicit references is found in the Chandogya Upanishad. Patanjali's Yoga Sutra prescribes ahimsa as the first of the five yamas (moral disciplines), which have universal applicability. In Gandhiji’s opinion, this message of ahimsa makes Hinduism particularly glorious. It is our duty to treat animals and even small insects with love and sympathy. Because of this noble sentiment many Hindus are vegetarians. By worshipping the cow the Hindus once again express their strong belief in the unity of all life.