Tapas, or austerity, is another important divine quality mentioned in the Bhagavad Gita (16.1). Austerities, as commonly understood, mostly relate to disciplining the body: standing in prayer in neck-deep water, standing with upraised arms, braving extremes of heat and cold, keeping vigils and observing fasts on auspicious days, giving up a favorite food after visiting a holy place, and so on. These physical practices could have some beneficial effect on the mind. But Swami Brahmananda says: "Those are not real austerities. Anyone can practice them. The body is easily controlled, but it is another matter to control the mind. It is very difficult to renounce lust and greed, to give up the desire for name and fame."
The word tapas means "heat." Tapas is practiced to purify the mind by burning the impurities within. Holy Mother Sri Sarada Devi practiced panchatapa, "the austerity of five fires." It involves sitting in meditation with four burning fires around, the midday sun burning overhead forming the fifth fire. Holy Mother, the embodiment of purity that she was, did not practice this austerity for attaining purity, but to set an example for others.
Sri Shankaracharya underlines the importance of tapas in his commentary on the Taittiriya Upanishad (3.1.1): "tapas is the best discipline, for of all the means that are causally related with definite ends, tapas is known to be the best. tapas consists in control of the external and internal organs." In other words, tapas is the best means to accomplish anything. This applies to secular as well as spiritual life. A study of the Vedantic view of human personality can help us understand the second part of the text in the commentary, which defines tapas as control of the external and internal organs.
According to the Bhagavad Gita (3.42), "The sense organs are superior [to sense objects and the body]; superior to the sense organs is manas [the mind]; superior to manas is buddhi [the discriminative faculty]; and superior to buddhi is He [the Atman]." There are five organs of action: the mouth, hands, feet, and the organs of evacuation and generation. More important are the five organs of knowledge: ears, skin, eyes, tongue and nose. They are so called because they bring us knowledge of the world through five perceptions: sound, touch, sight, taste and smell. The above ten visible organs have invisible, subtle counterparts, which make their presence felt in dream, when we perceive and act even though the external organs are not functioning. But the mind is the ruler of all the organs, since it can attach itself to any of them and make perception possible. manas is the deliberative faculty of the mind. It is usually fickle and restless. Superior to it is buddhi, the discriminative and determinative faculty of the mind, and the seat of decision-making and willpower. Buddhi helps us discipline manas. Superior to buddhi is the real Self, the Atman, the infinite, eternal substratum of the body, senses and mind.
In the perception of sight, for example, when rays of light from an object strike the retina, an impulse is carried to the brain, which transfers it to manas. Manas then presents it to buddhi, which scans previously stored impressions and sends back a reaction that goes successively to manas, the brain, the eyes, and the object. It all happens in a flash. This process is possible because of the Atman, the substratum of all. The other four perceptions take place similarly through the respective sense organs.