I. Introduction:
Nagarjuna is one of the greatest Buddhist scholars and practitioners of the second century CE. He is the founder of the Madhyamika school or the Middle Path School of Mahayana Buddhism. His writings include “texts addressed to lay audiences, letters of advice to kings, and the set of penetrating metaphysical and epistemological treatises that represent the foundation of the highly skeptical and dialectical analytic philosophical school known as Madhyamika.” 
The most important philosophical concept of Nagarjuna is the concept of Emptiness. This philosophy of Emptiness can be surveyed through his great text   Mulamadhyamakakarika, Fundamental Verses on the Middle Way. It is said that Nagarjuna is the second Buddha who appeared in the world to recover the true spirit of the teachings of Sakya Buddha which had been declined through many centuries of spreading and development. In the following sections we are going to analyze some of the most important verses in his texts to know more about his concept of Emptiness as well as his philosophy of the Middle Way.
 II. Main contents:
a. The No-self doctrine:
To understand Nagarjuna’s concept of Emptiness we must know that it was developed from the Buddhist doctrine of No-self. As a result we should first take a survey on what the doctrine of No-self is.
The doctrine of “No-self” is the most important and the most distinctive doctrine of Buddhism. It makes clear distinction between Buddhism and other self-based philosophies and theistic religions whose belief is that everything is created by God or controlled by God or gods. It is because of this teaching of No-self that Buddhism has been considered as an atheistic religion. Sometimes, people may think of Buddhism as a non-religious entity or as a philosophical system also due to this very doctrine of No-self. However, Buddhism has its religious aspects such as faith, belief, doctrines, and practices, etc. Buddhist scriptures mention a lot of divine realms which are understood as the realms of God or gods. Many Buddhist schools up to now believe in the effect of prayer; and for the followers of the Pure Land school, the Amitabha Buddha’s country is their destination realm, which may be thought as similar as God’s country in other theistic religions. The Buddhist doctrine of No-self thus “is both the most central and the most perplexing of all the teachings of the Buddha.” In the following sections we are going to discuss its essential content, what its duty is on the path to liberation, and why it is “so problematical to later Buddhists”?
According to Samyutta Nikaya, one of the most authoritative Pali texts of Buddhism, the essential meaning of the doctrine of No-self can be summarized like this: Human body and mind are just the compounds of five aggregates including body, feelings, perceptions, mental formations, and consciousness. The body is soulless because it is subject to sickness and change, and so do the other four aggregates. It would be impossible for people to say “Let my body be thus, let my body not be thus” and “Let my consciousness be thus, let my consciousness not be thus.” Let us take a look in what the Buddha addressed the monks dealing with this teaching of No-self: “What think you, monks, is the body permanent or impermanent? – Impermanent, Lord. – But is the impermanent painful or pleasant? – Painful, Lord. – But is it fitting to consider what is impermanent, painful, and subject to change as, “this is mine, this am I, this is my soul”? – No indeed, Lord.” The same inference can be applicable to feeling, perception, mental formation, and consciousness.  According to this teaching, everything has no permanent nature or identity because it changes continuously. If it had a permanent nature or self, it would not be changed. We can understand the Indian concept of atman or self as something which is permanent and thus it is never su