The period of early or pre-sectarian Buddhism lasted until about 100 years after the death of Gautama Buddha, when the schism into different schools started. The various splits that followed went together with the introduction and emphasis on abhidhammic literature. This literature was specific to each school, and arguments and disputes between the schools were often based on these abhidhammic writings. Early Buddhism, however, did not have Abhidhammic scriptures, except perhaps for a basic framework. The understanding of the essential early Buddhist doctrines and teachings - such as the Four Noble Truths, Dependent Origination and the Middle Way between existence and non-existence - is absolutely essential for the understanding of Buddhist thought. These doctrines are the heart of Buddhist thought and build the basis for all the schools and traditions. As such the lectures on early Buddhism build the basis for the study of Buddhism.