Tibetan Buddhism has four major traditions - Nyingma, Sakya, Kagyu, and Gelug. Although each one was transmitted from India at a different time, and through a different lineage, they all trace their origin back to the same source - Shakyamuni Buddha. And they all share the same ultimate aim, as they all teach authentic methods for achieving enlightenment for the benefit of all sentient beings. Therefore, when meeting with another tradition, a learned practitioner will never disparage the other's teachings, but instead would understand these as harmonious differences, and would have nothing but deep respect for them.
~ Chamtrul Rinpoche
(Chamtrul Rinpoche and his previous incarnations are from the Nyingma tradition of Tibetan Buddhism, the oldest school in Tibet. However, he has studied with many Buddhist masters from all four of the major traditions, and values each of them. Photographed a few years ago, the images are of Shakyamuni Buddha, His Holiness the Dalai Lama with Chamtrul Rinpoche, and with other members of the Sangha, including the then heads of these traditions)