The Venerable Dr. Parawehera Vajiranana Thera: "The Buddha's own conclusion in regard to the practical methods of mind training has been developed into two complex systems known as `cultivation of concentration,' and `cultivation of insight.' Again, these two systems correspond to the two predominant faculties, faith and wisdom. Those who have entered into the religious life through strong faith and devotion are trained in the Samadhi path which appreciates the special practice of rapt, absorbed, concentrated thought called Jhâna, the ecstatic tranquillity of mind. The method of jhâna meditation is called `the path of tranquillity,' and the disciple who has practised this path should enter in the end to the acquisition of that full knowledge which leads to Arhatship. Those who practise Samadhi meditation in the beginning, experiencing psychic powers as the aid of enlightenment, should practise insight at the end to attain Arhatship. Those who practise insight in the beginning, with or without Samadhi practice, will attain Arhatship. The Samadhi system, therefore, is optional in Buddhism, and is regarded as only a mental discipline preparatory to the attainment of full knowledge. But Vipassana being the direct path to full knowledge is indispensable and is universally imperative for the attainment of Nirvana. Hence insight meditation is the essential method of mental training in Buddhism and it is a unique system in Buddha's teachings. Thus ends an outline of the scheme of mental training explained in Buddhism as the only path to win the goal of man, the Eternal Happiness of Nirvana."
-- Notebooks Category 23: Advanced Contemplation > Chapter 7: Contemplative Stillness > # 298