For 必, there is another reading 畢, “all together,” adopted by Wang Hsi and Chang Yü. We now come to one of the most interesting parts of Sun Tzŭ’s treatise, the discussion of the 正 and the 奇. As it is by no means easy to grasp the full significance of these two terms, or to render them at all consistently by good English equivalents, it may be as well to tabulate some of the commentators’ remarks on the subject before proceeding further. Li Ch‘üan: 當敵爲正傍出爲奇 “Facing the enemy is _chêng_, making lateral diversions is _ch‘i_.” Chia Lin: 當敵以正陳取勝以奇兵 “In presence of the enemy, your troops should be arrayed in normal fashion, but in order to secure victory abnormal manœuvres must be employed.” Mei Yao-ch‘ên: 動爲奇靜爲正靜以待之動以勝之 “_Ch‘i_ is active, _chêng_ is passive; passivity means waiting for an opportunity, activity brings the victory itself.” Ho Shih: 我之正使敵視之爲奇我之奇使敵視之爲正正亦爲奇奇亦爲正 “We must cause the enemy to regard our straightforward attack as one that is secretly designed, and _vice versâ_; thus _chêng_ may also be _ch‘i_, and _ch‘i_ may also be _chêng_.” He instances the famous exploit of Han Hsin, who when marching ostensibly against 臨晉 Lin-chin (now 朝邑 Chao-i in Shensi), suddenly threw a large force across the Yellow River in wooden tubs, utterly disconcerting his opponent. [_Ch‘ien Han Shu_, ch. 34.] Here, we are told, the march on Lin-chin was 正, and the surprise manœuvre was 奇. Chang Yü gives the following summary of opinions on the words: “Military writers do not all agree with regard to the meaning of _ch‘i_ and _chêng_. 尉繚子 Wei Liao Tzŭ [4th cent. B.C.] says: 正兵貴先奇兵貴後 ‘Direct warfare favours frontal attacks, indirect warfare attacks from the rear.’ Ts‘ao Kung says: ‘Going straight out to join battle is a direct operation; appearing on the enemy’s rear is an indirect manœuvre.’ 李衛公 Li Wei-kung [6th and 7th cent. A.D.] says: ‘In war, to march straight ahead is _chêng_; turning movements, on the other hand, are _ch‘i_.’ These writers simply regard _chêng_ as _chêng_, and _ch‘i_ as _ch‘i_; they do not note that the two are mutually interchangeable and run into each other like the two sides of a circle [see _infra_, § 11]. A comment of the T‘ang Emperor T‘ai Tsung goes to the root of the matter: ‘A _ch‘i_ manœuvre may be _chêng_, if we make the enemy look upon it as _chêng_; then our real attack will be _ch‘i_, and _vice versâ_. The whole secret lies in confusing the enemy, so that he cannot fathom our real intent.’” To put it perhaps a little more clearly: any attack or other operation is 正, on which the enemy has had his attention fixed; whereas that is 奇, which takes him by surprise or comes from an unexpected quarter. If the enemy perceives a movement which is meant to be 奇, it immediately becomes 正. 4. 兵之所加如以碬投卵者虛實是也 That the impact of your army may be like a grindstone dashed against an egg—this is effected by the science of weak points and strong.