Four valid factors 四量（具量原典、具量闡釋、具量上師、具量覺受）
- valid scripture (lung tséma),
- valid commentaries (tenchö tséma),
- valid teacher (lama tséma), and
- valid experience (nyam nyong tséma).
They arose in this order, but in a student’s experience it goes the other way. First a student develops some valid experience, then appreciates the importance and value of a teacher. Once one has respect for the teacher one has more respect for the commentaries he or she teaches, and then for the original scriptures taught by the Buddha.