The living condition in material existence depends more or less on one’s intelligence and powerful living energy. Intelligence to counteract the hard struggle for existence is assisted by the senses for acquiring knowledge, and the living energy maintains himself by manipulating the active organs, like the hands and legs. But on the whole, the struggle for existence is an exertion of the mode of passion. Therefore all the sense organs, headed by intelligence and the living energy, prāṇa, are different products and by-products of the second mode of nature, called passion. This mode of passion, however, is the product of the air element, as described before.