If, in performing the great duty of non-injury and the other virtues auxiliary to it, a man be troubled by thoughts of sin, he should try to remove sinful ideas by habituating himself to those which are contrary to them. Thus if the old habit of sins opposed to virtues tend to drive him along the wrong path, he should in order to banish them entertain ideas such as the following:—“Being burnt up as I am in the fires of the world, I have taken refuge in the practice of Yoga which gives protection to all living beings. Were I to resume the sins which I have abandoned, I should certainly be behaving like a dog, which eats its own vomit. As the dog takes up his own vomit, so should I be acting if I were to take up again what I have once given up.” This is called the practice of _pratipaksha bhāvān_, meditating on the opposites of the temptations. A classification of sins of non-injury, etc., may be made according as they are actually done, or caused to be done, or permitted to be done; and these again may be further divided according as they are preceded by desire, anger or ignorance; these are again mild, middling or intense. Thus we see that there may be twenty-seven kinds of such sins. Mild, middling and intense are each again threefold, mild-mild, mild-middling and mild-intense; middling-mild, middling-middling and middling-intense; also intense-mild, intense-middling and intense-intense. Thus there are eighty-one kinds of sins. But they become infinite on account of rules of restriction, option and conjunction. The contrary tendency consists in the notion that these immoral tendencies cause an infinity of pains and untrue knowledge. Pain and unwisdom are the unending fruits of these immoral tendencies, and in this idea lies the power which produces the habit of giving a contrary trend to our thoughts. These yamas, together with the niyamas about to be described, are called kriyāyoga, by the performance of which men become fit to rise gradually to the state of jñānayoga by samādhi and to attain kaivalya. This course thus represents the first stage with which ordinary people should begin their Yoga work. Those more advanced, who naturally possess the virtues mentioned in Yama, have no need of beginning here. Thus it is said that some may begin with the niyamas, asceticism, svādhyāya and devotion to God; it is for this reason that, though mentioned under the niyamas, they are also specially selected and spoken of as the kriyāyoga in the very first rule of the second Book. Asceticism means the strength of remaining unchanged in changes like that of heat and cold, hunger and thirst, standing and sitting, absence of speech and absence of all indications by gesture, etc. Svādhyāya means the study of philosophy and repetition of the syllable “Aum.”