The Mādhyamika doctrine involving the Śūnya -vāda as in the Mahāyāna-sūtras is systematized by Nāgārjuna (A.D. 200?) as the Vijñāna- vāda of the Yogācāra was systematized by Maitreyanātha.

Āryadeva (c. A.D. 200-225), the author of the Catuḥ-śatikā is his worthy disciple, and one of the most prominent exponents of Nāgārjuna's masterpiece, Mūla- Madhyamaka-kārikā, is Candrakīrtti (c. A.D.  600-650).

Now the Mādhyamikas are those who followed the middle path of the Buddha. But what is this middle path?

It is well known that he preached a middle path in his first sermon, rejecting the two extreme views of excessive worldly enjoyments and too much self-mortification. But the middle path with which we are concerned here is quite different from it, as will be clear from the following lines.

In Sanskrit lexicons one of the names for the Buddha is Advaya- vādin “one who asserts not-two." Here according to the Mādhyamikas the word two in “not-two," refers to two ascertainments (antas), or views.

But what are these two views? They are such as existent and non-existent and eternal and non-eternal, self and non-self, and so on. That such views are harmful is abundantly clear in Buddhist literature, both in Sanskrit and Pali.

For instance, the Buddha is said to have declared:

“As mostly, O Kātyāyana, the people are engrossed in the notion of existence and non­existence, they are not emancipated."

And says Nāgārjuna :

“Those ignorant people who see existence and non-existence do not see the cessa­tion of the visible which is blissful.”

Again we read:

“It exists" this is, “O Kaśyapa, one definite ascertainment. But what is the middle of these two definite ascertainments cannot be denoted, cannot be illustrated, it has no base, nor any appearance, nor any mark, nor any denomination.

This is, O Kaśyapa, called the middle path by which there is the true examination of elements of existence."

So it is clearly declared that the Buddha having not accepted the two definite ascertainments taught his doctrine of the middle.

Therefore according to this view nothing is existent, nor is anything non-existent; nothing comes into being, nor does anything disappear; nothing is eternal nor has anything an end; nothing is identical nor differentiated; nothing moves hither, nor moves anything thither.

Thus as the followers of this School with which we are concerned here have accepted the middle path they are known as Mādhyamikas.

In the above discussion only two points, one positive and the other negative, are taken; but sometimes three or even four points are taken.

The idea of the rejection of both the opposite views of which the most important and well-known expressions are, sat (existent) and a-sat (non-­existent), is to be found even in the Ṛig-Veda (X. 129. 1): “There was neither the non-existent nor the existent." Gradually it was used also in the Upaniṣads and the Bhagavad Gītā (XIII. 12).

This position of the Mādhyamikas will be intelligible if one understands the law of dependent origination, i.e. the origination of things being dependent on the cause and conditions (pratītya-samutpāda).

This is implied in the Śūnya-vāda which is the central conception of the system. Let us explain it in the following few lines:

We say that every thing has its svabhāvainnate state" or “nature," as we say that heat is the svabhāva of fire. But what is it in reality? What is the characteristic of svabhāva?

It is that which is not fictitious (a-kṛtrima) and does not depend on others for its existence, nor comes into being afterwards having not been before.

Now heat which is generated by its cause and conditions, and comes into existence having not been before, and depends on others for its being, can in no way be the innate nature(svabhāva) of fire.

Consequently with regard to fire, that characteristic of it, if any, which in the three points of time, past, present and future does not deviate from it and being not before does not come into existence, and does not depend on others for its being, may alone be regarded as its own nature (svabhāva).

But is there anything of the kind of fire?

We say: “Neither it is, nor is it not." Yet, in order to remove the terror of untrained listeners, in practical truth, by imposition (samāropa) we say “it is."

But if you say that it is in its imposed form and in practical truth, of what kind is it then in reality in the absolute truth?

The answer is: “It is dharmatā, 'the state of being a dharma—the ele­ment of existence.'"

But what is dharmatā? Own-being (svabhāva). “What is own-being? Nature (prakṛti). And nature? That which is called voidness (śūnyatā). What does voidness mean? The state of being devoid of own being (naiḥsvābhāvya).

And what are we to understand by it? That which is suchness? (tathatā). What is this suchness?

Being such, that is, the state of being not liable to change (a-vikāritva), the state of remaining always (sadiva sthāyitā)”

“Accordingly we cannot say that heat is the svabhāva of fire. But as the non-origination of fire is independent of others and not fictitious, it is to be regarded as its svabhāva”

Now when there is no svabhāva of a thing it has also no origination, and owing to the absence of it, it has also no suppression.

Like fire, everything is devoid of its svabhāva as it itself has no existence.

This state of being devoid of svabhāva (naiḥsvābhāvya) is in fact meant by the word Śūnyatā in this system in such cases in the sacred texts as “sarva- dharmāḥ śūnyāḥ," “all elements of existence are void."

Things that appear to us do so not in their own characteristics but in those which are imputed.

Here a couplet quoted in a works declares that the truth of itself free from all imputations shines; and by such expressions as śūnyatā, all imputations thereupon are repudiated.

But unfortunately the sense of the word śūnyatā was much misunder­stood in the time even of Nāgārjuna himself, it being taken to mean annihilation (abhāva), or “non-existence” (nāstitā).

And it’s inevitable evil consequence led Nāgārjuna to write (XXIV. n):

Just like a snake or a science, taken in a wrong way, śūnyatā being misunderstood brings about one's destruction.

The objections that may naturally arise from this misunderstanding may thus be summarized from Nāgārjuna's own work (XXIV):

If everything is empty and there is no origination nor passing away, then there can also be no four truths of the noble, no rules of life based on the knowledge of those truths, no fruit of good and evil deeds, no doctrine of the Buddha, no monastic community, and finally also no Buddha.

Nāgārjuna meets all the objections resorting mainly, inter alia, to two truths, conventional(saṁvṛti-satya) and the highest(paramārtha-satya) as in the Vedāntic system of Śankara (here one additional truth being prātibhāsika-satya—the truth existing only in appearance).

He says those who do not understand the distinction between the two truths do not know the depth of the truth of the teaching of the Buddha.

Nirvana is not realized without knowing the highest truth (paramārtha) which cannot be instructed without following the every-day practice.

And if śūnyatā is understood in its actual sense there is no room for such objections.

This śūnyatā is the same as pratītya-samutpāda, which is nothing but the appearance of things owing to their cause and conditions, and this is in reality non-origination by their own nature. And here is the cessation of all expressions (prapañcopaśama).