The philosopher will be a karma yogi to the extent that he will work incessantly for the service of humanity and work, too, in a disinterested spirit. He will be a bhakti yogi to the extent that he will seek lovingly to feel the constant presence of the Divine. He will be a raja yogi to the extent that he will hold his mind free from the world fetters but pinned to the holy task he has undertaken. He will be a gnana yogi to the extent that he will apply his reflective and reasoning power to a metaphysical understanding of the world.
-- Notebooks Category 20: What Is Philosophy? > Chapter 5: The Philosopher > # 18