Twofold certainty 兩重確定（超戒寺教規：確定是佛陀的教法；確定是真實教法）
- establishing the certainty that what was being taught had actually been spoken by the Buddha; and
- establishing the certainty that what was being taught was the genuine and sublime dharma.
In this way they established the authenticity of both the teacher and the teaching. While the teaching style of Nalanda has been maintained down to the present day, the teaching style of Vikramashila no longer exists within Tibetan Buddhism.