There is the work of Ven. Medawachchiye Dhammajothi Thero: The Concept of Emptiness in Pali Literature which I thought is good to share.
transcript from the end of the book:
This Study on Sunnata (Skt. Sunyata) is mainly based on the Pali text. However, is is known that suyata came into prominence only with the rise of Madhyamaka philosophy of Acarya Nagarjuna. Therfore, no study of Sunnata is complete, without any reference to Sunyata as presented in Madhyamaka philosophy.
This study was done also with the objective of clarifying certain widely presented views regarding Sunyata. One of them is that this doctrine was not known to early Buddhism, or in other words, not a doctrine taught by the Buddha. This view gained so much of popularity, that scholars of the caliber of Stcherbatsky, followed by T.R.V. Murti boldly claimed this to be an innovation of Acarya Nagarjuna. Murti even went into the extent of comparing Acarya Nagajuna’s teaching an Sunyata as a ‘Copernican revolution’ in Buddhist tought. Therefore, besides explaining Sunna as found in the Suttas, an attempt has been made in this thesis also to show that this doctrine was well known to early Buddhism.
Thus, two whole chapter of this has been denoted to examine use of Sunna and other related terms in the suttas and in Post – canonical Pali literature. By enumerating and explaining such usage it has been possible to establish that this Sunna idea is not unknown to either the Buddha or to the disciples. However, the study shows that the terms Sunna/Sunnata are not of common occurrence as the term Anatta. It also came to light that even the disciples, though they knew what Sunna/Sunnata meant were far more familiar with the Anatta doctrine.
An attempt was made to examine how Sunya/Sunyata came into prominence overshadowing Anatta doctrine. In the present researchers view it is the early Madhyamaka texts like “Astasahasrikaprjnaparamita” etc., that contributed to the early popularity of these terms as a religious technical term.
These early Mahayana texts were in response to the non-Mahayana Buddhist schools that upheld the existence of some sorts of metaphysical entity that lay as the essence in everything. Of these schools the most prominent was the Sarvastivada school, and this belonged to the Therevada (=Hinayana tradition). This school in its attempt to explain reality, put forward a novel view which said that there is a self—nature (Sva-bhava) in everything, and that this Svabhava exists in all three periods of time namely, past present and future. The earliest criticism against this and other substantialist and essentialist views was by Mahayanists. In counter-arguing this view these early Mahayana texts highlighted the emptiness, voidness (Sunyata) of everything. It is, however, Nagajuna that made this his central thesis in presenting the Madhyamaka philosophy of his.
In this book an attempt has been made to show that Anatta and Sunya/Sunyata are not two different concepts. The present researcher is in agreement with the view that these two concepts cover the same range in their philosophical application; and that the preference for this term Sunya/Sunyata over Anatta only a shift of emphasis. The present researcher attempted to establish this point, citing textual and circumstantial evidence.
In doing this it has been attempted to demonstrate that the Buddh, too, used the term Sunna, and that he did so, not to bring out a new perspective but to further emphasize the absence of a self or anything connected with the self as the noumenon behind the phenomenon. In support of this textual evidence has been cited. It has also been shown that “Anatta” as used in early Suttas, did not merely mean the absence of an individual soul, but meant also the absence of any entity in both compounded (Samkhata/Samskrta) elements as well as in uncompounded (Asamkhata, Asamskrta) elements, that is Nibbana. Thus, it has been clearly shown that anatta means “emptiness” of everything, including Nibbana (Nirnvana).
Modern scholarship has attempted to sow that Acarya Nagarjuna gave a new interpretation to the Pratityasamutpada doctrine, and it is Acaeya nagarjuna that presented it as the central philosophy of Buddhism. It is true, according to the teachings of the present researcher, that Acarya Nagarjuny lays mere stress on the relativity aspect of Pratityasamutpada, while the early sutta forces more on its dependent origination aspect. Once again these are only different angles or perspectives from which the same doctrine is viewed. Paticca-samuppada/Pratitya-samutpada emphasis, both interdependence and relativity. In the final analysis these two aspects cannot be separated.
In early Sutta Paticca-sumppada was presented to explain causality, and in doing so the Buddha had to show that the then prevalent theories namly, self-creation, (Saya katam) external creation (Param katam) both self-creation and external creation, and also no causation or accidental causation (=Ahetu-appaccaya, Adhicca-samuppanna or yadrcchavada) are wrong. His explanation of Patucca-samuppada was focused on the rejection of these other causal theories.
Madhyamaka, however, emphasis the reality aspect of Pratityasamutpada and us it as a counter argument to nullify the Svadhava theory. Because of this Pratityasamutpada was considered more as an explaination of the voidness of everything. The two explanations namely, that of the Theravada Buddhist school and the Mahayana philosophy of the Pratitya-samutpada formula is not different in spirit thought the emphasis is different. And, of course, it has to be admitted that emphasis could vary according to the circumstance in which and the objective for which the formula is used.
Though some scholars attempt to show that it is Acarya Nagarjuna that raised Pratityasamutpada to the status of th central philosophy of Buddhism. The present researcher has attempted to show that early Buddhism to considered it to be so. For example, the content of enlightenment is often described as the knowledge regarding Pratityasamutpada. All other doctrines are based on and explained according to Pratityasamutpada. Beside, the “Kaccanagotta Sutta” very clearly calls it the preaching by the middle (Majjhena dhamma) which means it is the most-important central teaching. It should also be remembered that in the “Mahahatthipadopama Sutta”, Paticcasamuppada is equated with the Dhamma, which means it is the essence, the crux of the Buddha’s teaching. However it has to be noted, that it is Acarya Nagarjuna who made it prominent as the central philosophy of Buddhism without limiting in the explanation of Dukkha as it was in early Buddhism.
Beside, one should acknowledge also the fact that in early Buddhist Suttas Patipada is used in the sense of the way, the path or the practice and ‘Majjhima patipada’ is identical with the Noble Eightfold Path. But it is Acarya Nagarjuna who brought into light that that it is Pratitymutapada, which is the most fundamental of the Buddha’s Teaching, that even it provides the philosophical basis for the practice. The credit for highlighting the true spirit of the Buddha’s teaching is solely due to Acarya Nagarjuna.
A chapter was denoted to the study of various meditational practices recommended in early Buddhism, that lead to the realization of Sunna. Special focus was laid on two suttas namely Cula-Sunnata and Maha-sunnata both of the Majjhimanikaya. These while showing that the Buddha emphasized internalization of the understanding of the voidness of everything describes also how this could be done. This chapter will be of interest to those who wish it understand how meditative practice could be utilized to personally experience the voidness of all phenomena.
A chapter was devoted to show that it is not only the canonical Sutta that speaks of Sunna/Sunnata, but there is ample reference to it is post-canonical texts such as the Visuddhimagga. This chapter also brings to light that the Pali tradition was not unaware about the development of the sunya concept that was taking place in other non-Theravada traditions.
The present researcher’s study made it clear that the concept of Nibbana/Nirvana both in early Buddhism and Madhyamaka are similar; both advocate that Nibbana/Nirvana can be realized by correcting the distorted vision, driving out all “views” (drsti) that distort the proper understanding of reality. Both teachings hold that the final knowledge refers to the understanding of the true nature of things. To proper understanding in early Buddhism, is to see things as Anicca (impermanent) Dukkha (non-satisfactory/suffering), and Anatta (no-soul, no substance or essence). According to Madhyamaka this knowledge consists of seeing everything as empty, void (Sunya) of a Sva-dhava (self-nature). From this it is clear that thought there is a difference in terminology , in spirit both early Buddhism and Madhyamaka, advocate the same thing. This is further established by the fact that the Buddha also on an occasions advices that, one in order to escape this cycle of birth and death should see everything as empty (Sunnato lokam avekkhassu).
The major difference the present researcher sees between early Buddhism and Madhyamaka in their approach to Sunya is that the former lay more emphasis on personal experians in realizing the emptiness (Sunnata) of all phenomena, while the later emphasizes on logic and reasoning leading to an intellectual comprehension of it. However, that does not mean that Madhyamaka is not stressing the importance of internalizing this knowledge. The present research is of the view that Acarya Nagarjuna’s use of logic and reason is due to circumstance of the time, and the purpose for which his work Mulamadhyamakakarika was composed. It was composed not as a guide to practice but as acritical response for realists and substantialists. Hence, the preponderance of logic and reason.
Through this the present researcher found more tangible evidence to agree with the view of that Acaraya Nagajuna was not trying to present any new teaching but was making a concerted effort to remind the scholarship of the time that it is deviating from the teaching of the Buddha. The two stanzas of salutation for the Buddha, at the beginning and the end of this book, (Mulamadhyamakakarika) very clearly shows that Acarya Nagarjuna was a great follower and admire of the Buddha, and that he was attempting to highlight the true teachings (Saddharma) of the Buddha.