While there were debates among the astikas (who abides by Vedas), there were similar debates between astikas and nastikas (Buddhists, Jains).
The prerequisite of these debates was that you would understand the opponent’s position well enough to state it and then debate. Let’s understand the process better — let’s look at a refutation that happened 1300 years back. Here, it was Gaudapada (Adi Shankara’s guru’s guru) refuting four schools of Buddhism.
These were the Srautrantika, Vaibhashika, Yogachara Vijñānavāda, and the Shunyavada. All of them explored the question: is there an external world apart from us and came up with different points of view. We are a species that delight in metaphysical observations and can come up with darshanas that captivate and startle. In a dharmic venture, there is no monotheistic understanding. Instead, in trying to understand the world, these ambitious mind explorers came up with different explanations of reality.
The srautrantikas believed that when you perceive something it exists out there. For example, if you see a flower, it means that there is a flower right there in front of you. We also have unique experiences based on the object; the experience you have when you eat a mango differs from the experience you have when you eat roasted cashew.
This is what we experience daily, and it is natural to wonder how could anyone even have a position other than this? That’s where the Vaibhashika person comes and says hold on. We don’t see the flower just because it is out there, but because of the process that happens because of it. When you look at a flower, the eyes process that, and the mind creates an image of the flower. This is like the modern position that light waves hit our retina, resulting in some electrical activity in the brain creating the perception of the flower. The biological software processes signals from the biological hardware.
On hearing this, you can accept that it is a detailed and refined view than the srautrantika position. Now that we are here, what could be a position that could be a refinement of this?
The Vijñānavādin, brings a radical perspective — there is no external object. It is not like saying 2+2 = 5. The Vijñānavādin is saying there is no 2 or 5. Everything you perceive is just in your mind and what you feel as real is just an illusion. For example, in your dream, you will see new worlds and old friends, but the moment you wake up, all of that disappears. Vijñānavādin says the actual world too is similar, an illusion. If you thought that was rad, just see what the Shunyavadin has to say. The Shunyavadin takes it up a notch further and says that nothing exists. There is no external world, no mind. Nothing. Zilch. Nada. Everything is shunya.
If your mind goes into DEFCON 2, no one will blame you. We have ninety billion neurons entangled in a network of one hundred trillion synaptic connections. Only rishis with neurons which have seen the flashes of light between the extremities of darkness can come up with such darshanas.
To summarize, the Srautrantikas and Vaibhashikas, called the realists, agree that there is an external object, while the Vijñānavādins and Shunyavadins (the idealists) don’t. From now we will use this terminology.
Advaita is similar to Vijñānavāda. Gaudapada also argues that your waking world is like the dream world – a projection of the ultimate reality — Brahman. All of us, all the surrounding things are all are just names, forms, and behavior of Brahman. Now that the positions are clear, it’s time for Advaita to refute them.For that, Gaudapada uses a simple technique. Since the various Buddhist schools have been debating each other, he piggybacks on those arguments.
And so it starts.
The realist poses this question to the idealist. If you say that there is no external object, but just awareness, it seems odd. I can touch flowers, fruits, and feel happy seeing the Ram Mandir getting built. Each of these is a different perception inside me. If you say that there is one consciousness, then that conciseness is homogeneous. If consciousness is homogeneous, then the experience should also be homogeneous. Instead, our daily experience shows that diverse objects give us diverse perceptions. This means that there is a secondary object apart from this consciousness thing.
The idealist refutes it. The idealist rejects this from the standpoint of absolute reality. Look at a pot. If you have an external view, it will look like an object which exists. Now consider the same pot from the point of view of clay. There is nothing called pot, it is just a name, form, and behavior. Take a piece of cloth. It cannot exist without the thread, and you can say that the thread is the reality. The cloth is just a name and form imposed on the thread. Does the thread exist though? It is made of fibers and the thread is a name/form superimposition on the thread. Take it deep and deep and you end up with consciousness as the substratum on which everything else is a name and form. Hence, when you stand at the point of consciousness and look around, there is nothing else that differs from it.
The idealist continues: Hey, you realist, you had mentioned that it is diverse external objects which cause diverse experiences for you. In your dream world, you can eat an apple, drink lemon-soda, and experience happiness of the bhumi puja of Ram Mandir. In your sleep, all your sense organs have shut down. Your eyes are not seeing, your tongue is not tasting, and yet you have such diverse experiences such as all these. So saying that an external world causes diverse experiences is not true.
That works for the dream world, but what about the real world? Are we living in a Matrix to say that this is an illusion? Is this consensual hallucination? Gaudapada says, yes. Your waking world does not differ from the dream world. There is nothing apart from Brahman and whatever you see, feel and perceive is just Brahman with name, form, and behavior. This difference between the external and internal is all in the mind.
Now that the realists have been taken care of, Gaudapada turns towards the Vijñānavādins. So far he used the arguments by Vijñānavādins to refute the realists, but now it is time to take care of them. It might seem that Vijñānavādins and Advaitins were twins lost at the Kumbh Mela. Both of them claim that the world is illusory.
While that looks similar, there is one major difference. While Advaita says that Brahman is unborn, unchanging, and deathless, Vijñānavādins say that consciousness is momentary. If Advaitins think of Brahman as sunlight, always present and always shining, Vijñānavādins think of it as a strobe light, which flashes on and off. Reality is nothing but a stream of this consciousness hitting you at a fast rate creating an illusion of reality.
The problem here is that Vijñānavādins do not distinguish between consciousness and mind. They use the same word (Chittam) for both. When you experience a flower, a vritti is formed in your Chitta. When you smell the flower, you get another vritti. This happens at such a fast rate that it seems continuous. It is like a packet with awareness and context hitting you constantly. With meditation, you can slow down your awareness and see this happen in slow motion.
The Advaitin then asks, if consciousness is constantly born and dies, what leads to its birth again? Is it born from something which exists or something non-existing? Also, if what we perceive are flashes of consciousness, then how do you perceive the gap between two events? Is it blank? This does not sound right. The Advaita position is that just the vritti dies, but the consciousness never dies. Those who say that consciousness dies are looking for footprints of flying birds.
With all the three gone, the remaining one is the Shunyavadin. Gaudapada does not refute Shunyavada explicitly. Shankara in his commentary just mentions that they are like people who are trying to grasp the sky with their hands. A later debater says that if everything is empty, then you, Shunyavadin are also empty and hence there is no need to debate you.
These back-and-forth arguments illustrate the rigor of arguments among the various darshanas. Going through this process helps us understand each of the darshanas clearly. The people who discovered these darshanas because of their tapas are no longer with us, but these discoveries are still being talked about and they still captivate and startle.