For a full and unobstructed unfoldment of the mind's capacities, the influence of two complementary forces is needed: of activating and restraining. That two-fold need was recognized by the Buddha, the great knower of mind. He advised that the Faculties of Energy (viriy'indriya) and of tranquil Concentration (samadh'indriya) should be kept equally strong and well balanced. 1 Furthermore, He recommended three of the Seven Factors of Enlightenment (bojjhanga) as suitable for rousing the mind, 2 and another three for calming it. 3 In both cases, among the Spiritual Faculties and the Enlightenment Factors, it is Mindfulness (sati) that not only watches over their equilibrium, but actively stimulates the growth of their activating as well as their restraining power.