Pali Canon and Agama

Chade-Meng Tan summarized here from a talk by Bhikkhu Bodhi (audio talk here):

Most of the records of the teachings of early Buddhism were lost with the demise of Buddhism in India.

Fortunately, 2 lines of transmission occurred and survived. The 1st was the Pali Nikayas, which survived in Sri Lanka via the Theravada school of Buddhism, which thrived there. The 2nd was the Agamas, which passed from northern India to China.

Each of these contains 4 collections, with names carrying largely identical meanings in Pali and Chinese:

1. Digha Nikaya (长阿含经), collection of long discourses.
2. Majjhima Nikaya (中阿含经), collection of middle-length discourses.
3. Samyutta Nikaya (杂阿含经), collection of themed discourses.
4. Anguttara Nikaya (增一阿含经), collection of “increase by one” discourses.

The main difference between the Nikayas and Agamas: All the Nikayas are from the same school of Buddhism, which is the Theravada school. In contrast, the Chinese translators chose the collection from a different school for each Agama. For example, they chose the Dharmaguptaka version of the long discourses, the Sarvastivada version of the middle-length discourses, and so on. There are some differences between the nikaya and agama collections. The order of the discourses are not always identical. Also, some discourses that are assigned to one collection in the nikayas are assigned to another in the agamas => assignments are not identical.

You may also be interested in the sub-chapter "3.1 Comparative Studies" from the book "The Authenticity of the Early Buddhist Texts" by Bhikkhu Sujato and Bhikkhu Brahmali.

I quote from it here:

In addition to the full scale study of the Majjhima Nikāya, there have been multiple smaller studies of various parts of the EBTs. These have confirmed that all the EBTs share a similar level of agreement to what we find between the Suttas of the Majjhima Nikāya and its parallels. Such studies have been carried out for substantial portions of the Saṁyutta Nikāya/ Saṁyukta Āgamas, and to a lesser extent for the Dīgha Nikāya.

Caution needs to be exercised, however, regarding the Ekottara Āgama, which is nominally the collection corresponding to the Pali Aṅguttara Nikāya. Although it shares some significant structural features with the Aṅguttara, the content is often very different. The text is highly erratic and internally inconsistent, possibly being an unfinished draft. Scholars agree that it includes proto-Mahāyānist additions, thereby establishing its late date of completion compared to the rest of the EBTs.

This high degree of correspondence among the EBTs across different lines of transmission does not exist for any other texts of the vast Buddhist corpus. Even in the stylistically oldest part of the Khuddaka Nikāya, suchas the Sutta Nipāta, the Udāna, and the Dhammapada, there is substantial divergence between the schools. This is despite the fact that these texts do have a common core, which is found across the different traditions. With texts such as the Abhidhamma, despite a small common core, the divergence is even greater. But the vast majority of Buddhist texts are exclusive to the individual schools and do not have any parallels at all.

This means that the Majjhima Nikaya, Samyutta Nikaya and Digha Nikaya are largely the same between the Pali suttas and the corresponding Agamas.

The Anguttara Nikaya and Ekottara Agama are not the same as the latter has proto-Mahayanist additions.

Meanwhile, the Kuddhaka Nikaya (Sutta Nipata, Udana, Dhammapada etc.) is very different in the Pali suttas and the corresponding Agamas.

Here is an excerpt from Ven Sujato, The Pali Nikāyas and Chinese Āgamas:

These studies have largely confirmed Beal’s initial hypothesis – the Chinese Ᾱgamas and the Pali Nikāyas are virtually identical in doctrine. They are two varying recensions of the same set of texts. These texts – popularly referred to simply as ‘the Suttas’ – were assembled by the first generations of the Buddha’s followers, before the period of sectarian divisions. They are pre-sectarian Buddhism.

Although in the popular mind these texts are thought of as ‘Theravāda’ teachings, this is not so. Eminent scholar David Kalupahana went so far as to declare that there is not one word in the Pali Nikāyas that represents ideas peculiar to the Theravāda school (although I think this is a slight exaggeration.)

Another example, this answer on this site refers to this scholarly paper -- which analyses two versions of the same sutta (one Pali, one Chinese) -- and finds they are almost identical, with (if I remember rightly) only one line of difference. In fact the paper's authors argue that in this case it's the Chinese version which is probably the more authentic/original.

The bottom line is though that they're often the exact same suttas, albeit in different languages and possibly slightly altered through the ages.

And they're doctrine common to Mahayana and Theravada -- although, I don't know, perhaps someone mentioned on this site that some Mahayana schools tend to study summaries or commentaries (which they call "abhidarmas") of the agamas.

Though apparently (perhaps not surprisingly) the collections are not quite identical, Wikipedia mentions:

Large parts of the Anguttara nikāya and Samyutta nikāya do not occur in the āgama, and several sutras/suttas are dissimilar in content.

Perhaps (I'm not sure -- I haven't studied the agamas) it's more accurate to say that the agamas are a large subset of the Pali Nikayas.

A more useful way of looking at it is to see both the Nikayas and Agamas as Early Buddhist text rendered in different languages (Pali for Nikayas, Sanskrit for Agamas). If you've read Ven. Analayo's work on comparative studies between the two systems, you'll see they are very very similar. Now, Theravada pretty much focuses on the Nikayas as their go-to sutta sources, while Mahayana, due to its vast number of sub-schools or sub-systems, has various focuses depending on the particular school. Some pay more attention to the Agamas, while others more on the later additions (Amitabha collections, Avatamsaka, Lankavatara, Prajnaparamita, etc...).