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Basic teachings

Apart from the middle way, certain basic teachings appear in many places throughout these early Buddhist texts, so older studies by various scholars conclude that the Buddha must at least have taught some of these key teachings:

According to N. Ross Reat, all of these doctrines are shared by the Pāli Canon of Theravāda Buddhism and the Śālistamba Sūtra belonging to the Mahāsāṃghika school. A recent study by Bhikkhu Analayo concludes that the Theravādin Majjhima Nikāya and the Sarvāstivādin Madhyama Āgama contain mostly the same major Buddhist doctrines. Richard G. Salomon, in his study of the Gandhāran Buddhist texts (which are the earliest manuscripts containing discourses attributed to Gautama Buddha), has confirmed that their teachings are "consistent with non-Mahayana Buddhism, which survives today in the Theravada school of Sri Lanka and Southeast Asia, but which in ancient times was represented by eighteen separate schools."

However, some scholars such as Schmithausen, Vetter, and Bronkhorst argue that critical analysis reveals discrepancies among these various doctrines. They present alternative possibilities for what was taught in earliest Buddhism and question the authenticity of certain teachings and doctrines. For example, some scholars think that the doctrine of karma was not central to the teachings of the historical Buddha, while others disagree with this position. Likewise, there is scholarly disagreement on whether insight into the true nature of reality (prajña) was seen as liberating in earliest Buddhism or whether it was a later addition. according to Vetter and Bronkhorst, dhyāna constituted the original "liberating practice", while discriminating insight into transiency as a separate path to liberation was a later development. Scholars such as Bronkhorst and Carol Anderson also think that the Four Noble Truths may not have been formulated in earliest Buddhism but as Anderson writes "emerged as a central teaching in a slightly later period that still preceded the final redactions of the various Buddhist canons."

According to some scholars, the philosophical outlook of earliest Buddhism was primarily negative, in the sense that it focused on what doctrines to reject and let go of more than on what doctrines to accept. Only knowledge that is useful in attaining liberation is valued. According to this theory, the cycle of philosophical upheavals that in part drove the diversification of Buddhism into its many schools and sects only began once Buddhists began attempting to make explicit the implicit philosophy of the Buddha and the early texts.