The philosophy of Shri Shankara is called non-dual (Advaita). Sometimes it is called the doctrine of unity, but erroneously, for unity is the cause of duality. If one assumes unity, one tacitly assumes multiplicity.
The Sankhya system of philosophy, which is the basis of the Yoga system of Patanjali, is essentially dualistic, and it was to repudiate this widely accepted philosophy that the holy philosopher Shankaracharya called the Upanishadic thought non-dual. Every man in the street, every child, every lunatic believes in duality. How easy it is to state that there is a God and matter, each independent of the other, good and evil struggling for supremacy! Aristotle’s four basic elements and Plato’s plurality of souls are the common experiences of every day. Everyone knows that one has five fingers on each hand. One need not be a philosopher to believe in duality.
The glory of the holy Veda is the truth of non-duality, which, though contradicted in everyday experience, is established by the super-conscious experience and logically is sounder than the doctrine of multiplicity.
Advaita only means negation of duality. In fact when it is said that Brahman, the cause of the origin, maintenance, and withdrawal of the universe, is Advaita (i.e. non-dual), it means that it transcends all conceptions, positive and negative. Nothing positive can ever be imagined or said about it. It was to expose this fallacy of the Sankhya philosophy, and the Buddhist and Jaina philosophers, and the materialism of Charvaka, that holy Shankara said: “Brahman is non-dual”.
Sometimes Brahman is spoken of as Sat-Chit-Ananda, that is, existence absolute, consciousness absolute and bliss absolute. The author of Panchadasi, Mahamuni Vidyaranya Swami, says that Sat or existence absolute means that Brahman is not Asat or non-existent. Chit means that He is not unconsciousness. Ananda means that His nature is not suffering. According to this great philosopher, a follower of Shri Shankara, nothing positive can be stated about Brahman. In one of the Upanishads the disciple says to the Master: “Lord, tell me the nature of Atman”. The Teacher remains silent. Again the question is asked, and again the answer is silence. By his silence the Teacher indicated that the nature of Atman is inexplicable, indescribable and unimaginable. The well-known expression from the Upanishads ‘neti, neti—not this, not this’, is echoed by Spinoza.
This fact should be borne in mind by every student of Yoga, and he should write in bold letters in his study: “Ekam evam advaitam. Neha nanasti kinchina—He is the One without a second. There is not the least shadow of multiplicity in Him.” When you hear anybody, be he a Plato or a Descartes, who expresses the reality of more than one existence, bless him and leave him alone, because he is sure to entertain you with nonsense.
Some people will try to show that there is duality in the Yogic doctrine and will quote the example of Maya and Brahman, Jagat (world) and Ishvara (creator), Guru (teacher) and Shishya (disciple), the holy rituals, traditions, the three worlds, the three bodies and so forth. Tell them that this seeming duality is a hypothesis, not to establish duality, but to disprove it. If you meet one who claims to teach the spiritual truth, ask him frankly if his doctrine is Advaita. Have nothing to do with him if it is not so. We cannot tolerate darkness or error, and all except Advaita is one colossal error.
The author of Vicharasagara (Ocean of Enquiry), Nischal Das, says: “He is a Guru who teaches the non-duality of Brahman. Even if one is able to create a new sun and moon, it means nothing if one teaches duality.” A common epithet applied to the Gita is Advaita amrita varshani (the cloud that rains the nectar of Advaita). Let it also be stated that Brahman is neither dual nor non-dual; holy Vasishtha says: “Some say He is dual, some that He is non-dual; they do not know Shiva, who is above duality and non-duality”. Consult your own experience. Do you think that you are two or one? Nobody believes himself to be Siamese twins. Even if the whole world tried to convince you that you are two, you would still say: “No, I am one”, and you are Atman.
Maya does not infringe the truth of non-duality, as the forms of a chain, a ring or an ear-ring do not make the gold, of which they are made, many. Shri Hari is One without a second. He has not become many. The waves arising in water do not make the water multiple. Meister Eckhart, the prince of German mystics, proclaims Advaita; so do the Sufis and the Chinese Taoists. In fact, it is the doctrine of all those who have known truth.
“All eyes are my eyes; I am beating in the hearts of all; I am the pupil of the eyes of all”—so sings the God-intoxicated Rama Tirtha. Tulsi, Kabir and Nanak, Sur Das and Shri Dada all sing to the tune of non-duality. A man saw in a dream that he was holding the head of Satan in one hand and hammering on his beard with his fist. When he awoke, he found that he was holding his own beard.
The One existence, whose nature is Bliss, pervades all phenomena. To see it, is to be cured of the blindness of ignorance. A disciple of Shri Dada is a Brahmin, a Buddhist, a Christian, a Moslem, and a scientist at the same time. He worships Him in all temples and churches; he condemns none, he loves all.