What is the origin, meaning and purpose of human existence according to the esoteric teachings of Tantric Buddhism? Is it possible to achieve spiritual realization without having to renounce, as a monk or nun, life in the world? What is the secret of all enlightened beings, the heart of every way of salvation, beyond religious, racial or caste divisions? The first part of the Hevajratantra, here translated and commented, tries to answer these questions in an organic and didactic way. Although the work was composed in India between the XNUMXth and XNUMXth centuries, in a social and cultural context very far from ours, the essence of its message, properly translated and interpreted, is extraordinarily current.