Tapas is analysed by domain before it is analysed by guṇa. Bodily austerity (17.14): worship of the gods, the twice-born, teachers and the wise; purity, uprightness, celibacy, non-violence. Austerity of speech (17.15): words that cause no distress, that are true, pleasant and beneficial, together with the practice of recitation. Mental austerity (17.16): serenity of mind, gentleness, silence, self-restraint, purity of disposition. This is a beautifully complete map — discipline of deed, word and thought. And each domain is then itself threefold (17.17–19): austerity done with faith and no craving for fruit is sattvic; done for honour, respect and display, unstable, is rajasic; done with self-torture, or in order to harm another, is tamasic. The last is a pointed warning — austerity is not sanctified by mere severity; penance performed to injure oneself or others is the darkest kind, not the highest.