(9.16) Since for you Chittamatrins such illusion-like forms do not exist,

How do forms exist?

Instead of directly refuting the question posed by the Chittamatrins, the Prasangikas flip the tables and ask the question how then in their system do forms exist? Why do the Prasangikas do this? The Prasangikas are known as consequentialists. What this means is they will expose absurd consequences of the positions asserted by the other schools as a way of demonstrating that their tenets are not tenable.

(Chittamatrin) “Although forms do not exist as external objects, they do exist in another way –

A form is an aspect, the nature of the mind to which it appears.”

It is very important to get to know exactly how things exist in the Chittamatrin system. The final view of emptiness – the Tantra Prasangika view – is actually the union of the Prasangika and Chittamatrin view.  What is the Tantra Prasangkika view? The Prasangika part says that all phenomena are mere projections of mind, and the Chittamatrin part says that these appearances themselves are the nature of mind. More profoundly, the Chittamatrin part says that all phenomena are the nature of mind, specifically the mind of great bliss, and the Prasangika part says that the mind itself is empty of inherent existence.  Here, the Chittamatrins say that external objects do not exist but that forms are the nature of the mind to which it appears. The Tantra Prasangika view entirely agrees. External objects are objects that exist independent of the mind. Such objects do not exist in either the Chittamatrin view or the Prasangika view. But how do forms exist? They exist as aspects of the mind. They are like waves on the ocean. Just as you cannot separate a wave from the ocean, so too you cannot separate a wave-like form from the ocean of its mind.

(9.17) You Chittamatrins assert that mind itself appears in the aspect of form.

If this is so, how does the mind arise?

Buddha, the Protector of the World, has said

That the mind cannot behold itself.

(9.18ab) For example, just as the blade of a sword cannot cut itself,

So a mind cannot behold itself.

Where the Prasangikas and the Chittamatrins disagree is on the nature of the mind itself. The Chittamatrins say that the mind truly exists. The Prasangikas say that the mind is also empty. The Prasangikas do not disagree that phenomena are aspects of or are the nature of mind, they simply disagree about the ultimate nature of the mind itself.

The fundamental question the Prasangikas ask of the Chittamatrins is how does the mind arise or come into existence? Since the Chittamatrins say that the mind truly exists the question becomes how does it come into existence?  The answer the Chittamatrins give is the mind knows itself. How is this an answer? Both Prasangikas and the Chittamatrins agree that objects only exist if they are known by a valid mind. Therefore, they seek to establish the existence of the mind that has the ability to know itself – which is called a self-cognizer. The entire debate between the Chittamatrins and the Prasangikas revolves around the existence of self-cognizers.  If the Chittamatrins cannot establish a mind that knows the truly existent mind, then they would have to agree that a truly existent mind does not exist because there is no valid mind that knows it. The Prasangikas therefore refute the possibility of a mind that knows itself.

Their first refutation is scriptural authority in which Buddha says that a mind cannot know itself.  The analogy given in the scriptures is just as a blade cannot cut itself so too a mind cannot know itself.

(9.18cd) (Chittamatrin) “On the contrary, just as a lamp can illuminate both itself and the objects around it,

So the mind can behold both itself and other phenomena.”

The Chittamatrins argue as an analogy that just as a lamp can illuminate itself and all the phenomena around it, so too the mind can know itself and other phenomena. A light simply illuminates all things, including itself.  In the same way, the mind simply knows all things, including itself.  

(9.19ab) If a lamp illuminates itself, then darkness obscures itself,

And it follows that no one can see darkness because it is obscured!

Here the Prasangikas try to expose an absurd consequence that follows from believing the Chittamatrin position.  Since light and dark are relative concepts, opposite of one another, if it is true that a light illuminates itself then it follows that darkness obscures itself. Why is this true? Darkness is the absence of light, but if it is an existent it must still be something that is known. So if light knows itself then how does darkness know itself? Darkness is the nature of obscurity and so therefore it would follow that darkness obscures itself, at which point it could not be known. Therefore, there must be something that sees the light and sees the darkness that is separate from the light and the darkness itself. In the same way, to know a mind there must be something else that knows it.  It can’t know itself.

Further, it is incorrect to say that light illuminates itself. The light of a lamp may illuminate the lamp that holds the light, but the light itself does not illuminate itself it is simply the nature of luminescence. In the same way the mind does not know itself, it is simply the nature of knowing.