


The Tao Te Ching,
, the "Classic of the Way and Virtue" (or, the "Power of the Way," the "Way and Its Power," etc.), is the first and principal Classic of Taoism. It is handed down with a division into two books. This was often thought to be an arbitrary division; but recently a manuscript was discovered in which the order of the two books was actually reversed. An interpretation has now been offered that the two books are intended to be about the Tao [
] and Te [
], respectively. Book I does begin with statements about the Tao, and Book II with statements about Te. Since the Tao might be thought to be more important than Te, the format that reverses the books may then simply reflect that judgment, with the treatment of Te as an introduction or preliminary to the Tao. It is not clear that reversing the order would really make any difference in the teaching.
Joanna C. Lee and Ken Smith, who have a good translation and provide both characters and a Pinyin transcription (all but unheard of in other translations), simply break the Tao Te Ching into two separate little books, The Pocket Tao, Lao Tzu's Classic of the Way [A Museworks Book, Pocket Chinese Classics, 2012] and The Pocket Te, Lao Tzu's Classic of Virtue [A Museworks Book, Pocket Chinese Classics, 2013]. The order in which to read these is thus up to the reader.
This webpage originally wrote up the comments I would make in my Introduction to Philosophy and Asian Philosophy classes, from 1987 to 2009, and so sometimes comments are directly addressed to students. The classes used the D.C. Lau translation: Lao Tzu, Tao Te Ching [Penguin Books, 1963]. Over the years maintenance of the page has involved adding material, especially Chinese text, and more in the way of critique of the translations by Lau and others. Translating the Tao Te Ching is a challenge, as examined in detail for the first chapter below.
After this page was first on line, and most students still had no access to the Internet, the Valley College Bookstore would print out and bind copies of the file, which students could purchase. Soon, however, people could sit in class with their own laptops and read the webpage during the lecture. The phenomenon was just beginning, of background noise in classes, with people typing notes on their laptops, before I retired in 2009.
Verse 1: "The Way that can be spoken of, Is not the constant way." The Tao Te Ching begins with a pun: "Way" and "spoken of" ("said") are the same character,
. So the first line says: "The Tao that can be tao-ed is not the constant Tao." Next we get a similar pun with, "The name that can be named..." Here the pun can be maintained in English, where "name" can be both noun and verb, as with Chinese
.
The quality or preconceptions of a translation of the Tao Te Ching can usually be determined from the rendering of these lines. Those determined to unpack the meaning of Taoism in the translation, according to their own interpretation of Taoist doctrine, will often render these terse sentences into a paragraph, sometimes with irrecognizable renderings of the key words. The affection of a translator for Taoism cannot excuse a method that only obscures the nature of the text itself.
Let's look at some translations, old and recent, of just the first six characters.
The worst temptation here was an interpretive, rather than literal, rendering of
, like "Reason" or "Nature." A serious question about translation is with tào as a verb. Since the noun can mean "road, way, path," Legge, Mair, Le Guin, and Muller are all tempted to produce a corresponding verb, "tred," "walk," "go," or "follow" -- which I have indicated with "!!". However, although Mathews' Chinese Dictionary [Harvard, 1972, pp.882-884] gives verbal meanings for the character as "speak, tell" (or even "lead, guide"), "tred," "walk," "go," or "follow" is not among them. Interestingly, no one has tried the translation, "The Tao that guides is not the constant Tao." The feeling seems to be that the Tao does guide. Indeed, in Chinese philosophy a "Way" means the actions recommended by any particular school or teaching, not just Taoism. On the other hand, if the line denies that the Tao can be followed, this would seem to void the entire purpose of a Taoist teaching. By Not-Doing, 
, after all, one can "tred," "walk," "go," or "follow" the Way. The approach that began with Legge would deny the possibility, not of speech about, but of conformity to the Tao. This does not otherwise appear to be the thrust of the teaching. Indeed, if the Way is something that cannot be followed, how can it be the Way? And what are we supposed to do instead? Indeed, we do nothing, but then that is precisely what following the Way is. So by not following it, we follow it. The renderings that are the most interpretative rather than simply translating are Bahm, Ni, and Roberts. Roberts seems to be at pains to take "way" in its simplest and most literal meaning, and not as referring to the hidden and obscure entity, the force behind "not doing," that everyone else takes the Tao to be. But construing the sentence his way requires an awkward locution and liberties with the wording. Lee and Smith return to the simplest and most faithful rendering -- while also giving us the Chinese text and a Pinyin transcription, the latter or both of which are missing from most other editions.

, "The nameless." The Tao is really nameless. Why it is called the "Tao" we will see later. This matches the verse about the Tao, with
, "name," as noun and verb in place of "tao" as noun and verb.
Verse 8: "Not to honour men of worth will keep the people from contention; not to value goods which are hard to come by will keep them from theft; not to display what is desirable will keep them from being unsettled of mind." We might think that honoring the worthy would encourage them and others who might aspire to worth. But the Taoist worries about the conflict that could result between contenders for honors. Indeed, the Taoist would not seek honor in the first place, since it would mean putting himself forward when the Tao really accomplished whatever needed to be done. So the Taoist ruler will act like the men of worth themselves desire no honors. Next, if you do not wish to obtain valuable goods, or to value them yourself, then people will see no reason to become robbers. In the next statement there is a question about the translation. Where D.C. Lau says "not to display what is desirable," Joanna C. Lee & Ken Smith say simply, "Eschews desires." "Display" seems to be what doesn't go with the characters, and we could even translate the four characters as "Do not (even) see what you might desire." This means avoiding desires, which would be a Taoist sentiment. Then, if the ruler has no desires, disorders (not just being "unsettled of mind") will not arise among the people. As in Confucianism, the actions of the ruler set the pattern for the people. With the Taoist ruler, we may have an ambiguity that either we want the people to not even notice the ruler, or we want the people to notice that the ruler has no desires and does not value things that might arouse competition and conflict in the people.
He always keeps them innocent of knowledge and free from desire." Unfortunately, at least part of this sounds too much like modern government, which can "empty their minds" with modern "education" and "weaken their wills" with unavoidable bureaucracy and arbitrary authority, while actually neither feeding them nor strengthening bones. Thus, the hunger in Venezuela does not seem to bother American partisans of the regime, including Members of Congress, which properly makes us wonder what they really intend. For the Taoist ruler, keeping the people ignorant and "free from desire" is supposed to allow them to flourish under the Tao. However, this is as likely to make them inert, which will not benefit them. But unlike the modern politician, the Taoist ruler at least makes no attempt to instill fear, obedience, and control. He should be invisible.
placed by D.C. Lau with verse 9, is translated by Joanna C. Lee & Ken Smith in conjunction with the next statement, in Lau's verse 10. The translation is also a bit different, with Lee & Smith saying, "Even the ambitious dare not go too far." I think "clever" might be closer here than "ambitious," and it looks like "never dare act" is more like it than "dare not go too far." Note that the terms used here are not those for the Taoist sage, who is called "sacred," while whoever this is merely has knowledge. Thus if we translate
as "wisdom," it will be more the kind of wisdom that St. Paul regards as inadequate or deceptive: "If any one among you thinks that he is wise in this age, let him become a fool that he may become wise" [1 Corinthians 3:18]. Sounds very Taoist.
We might note with this principle that the expression 

literally can mean "do not-doing," which means that "not doing" is indeed something that one can "do" -- although
can also mean "by means of," which will also work (we can even strengthen that by changing the tone,
, now "for, because of, on account of"). Also of particular interest is the final character,
, which first of all can mean "to cure, heal," but then "to govern, regulate, put in order," and finally, "the result of the previous, the peace under good government" [Mathews' Chinese Dictionary, Harvard, 1972, p.141]. The choice of this character can thus imply that the whole expression is not just talking about Taoist practice in general, which may apply to the hermit or mendicant, but specifically to government. In different translations, we thus may see this rendered in slightly different but interesting ways, mostly ignoring the double negative. D.C. Lau says "order will prevail," Joanna C. Lee & Ken Smith says, "sustains the natural order," and Man-jan Cheng & Tam C. Gibbs say, "well regulated" [Lao-Tzu: "My words are very easy to understand", Lectures on the Tao Teh Ching by Man-jan Cheng, translated by Tam C. Gibbs, North Atlantic Books, 1981, p.29].


. Although Taoism sometimes sounds very pacifistic, it is possible to wage war on Taoist principles; and here it is recognized that nature, and so the Tao, is not always kind (
). Indeed, "ruthless" here translates
, "not kind," "not benevolent," or "not humane." Roger T. Ames and David L. Hall in their "philosophical translation" apparently don't like the implications of this, so they translate the verse as, "The heavens and the earth are not partial to institutionalized morality" [p.84]. This might indeed be a Taoist sentiment, but it is perhaps an over-interpretive reach as a translation of a line with only four characters. In a footnote, their justification of it is that rén represents "a suspect Confucian value that emerges only when genuine moral feeling has been overwritten by conventionalized rules of living" [p.206]. This is not quite right. The substance of the Confucian virtue is not suspect; it is that the virtue is subverted by Confucian speech about it. Is that the implication here? It doesn't look like it to me. The more sensible reading is the obvious one, that nature is not always benevolent, as indeed it is not. On the other hand, whatever the interpretation ought to be, the purpose of a translation is to render the plain meaning of the original, not to obscure it with an editorial. The worst feature of the Ames and Hall "translation" is that it is impossible to tell even remotely what the original wording would have been. The reader is simply not allowed to interpret the text for himself. The statement further, that Heaven and Hearth treat the people as "straw dogs," is easily conformable with the "not kind" translation. What it is about "straw dogs" is not spelled out and is subject to varying interpretations, but it doesn't sound good. We also get this all repeated in terms of 

, "The Sage is not kind." Ames and Hall also want to the Sage to not be "partial to institutionalized morality," as he would not; but he also treats people as "straw dogs." The general error of Ames and Hall, that Taoism doesn't want to cite any Confucian virtues, is contradicted in Chapter XIX, where we learn that the "people will again be filial." That is really the key to the paradoxes of Taoism.
, imagery of the Tao Te Ching. While the Tao is beyond the opposites of yin and yang,
, the principles of Not Doing (
) and No Mind (
), which allow the Tao to operate, have a much greater affinity with yin (passive, receptive) than with yang (active, aggressive). The Tao Te Ching therefore illustrates Not Doing with extensive yin imagery. Here the "valley" (
), the "female," and perhaps the "gateway" are all yin images.

, Japanese shônen) puts his person last and it comes first....without thought of self that he is able to accomplish his private ends?" If someone pursues their self-interest (practices the "doing" of self), they defeat and destroy it. By practicing Not Doing, the sage therefore allows the Tao to pursue his self-interest for him, which it will do. This all explains why the sage Lao Tzu,
, the presumptive author of the Tao Te Ching, may not have existed: the author or authors of the Tao Te Ching would not put themselves forward to claim authorship. That would not be putting one's "person last." It would be a much more Taoist move to deny authorship and attribute the book to the "Old Master," which is what "Lao Tzu" means. Whether one author or many, critical references to Confucian doctrine in the book (especially Chapter 38) imply that it was written during the Warring States Period, while the tradition is that Lao Tzu was a contemporary of Confucius -- that they even met.
"Highest good is like water." The supreme yin image of the Tao: Water. Nothing is so essential to life, and so yielding and receptive; but water is also tremendously powerful and irresistible, as the Chinese know well from devastating floods of the Huang He and Yangtze rivers. "Settles where none would like to be." Water goes to the lowest position, which is not a status that people commonly fight over. Thus Not Doing avoids conflict, "does not contend."
"Next comes one with whom they take liberties," like the younger son who succeeded Shihuangdi and was overthrown.
The translation of this passage is vulnerable to wildly different interpretations. Thus, it begins with two characters, 
, that can mean several things. James Legge renders it as "in highest antiquity," but then he proceeds to interpret the reference as otherwise to the ancient and best rulers [op. cit. Dover, 1962, p.60]. Forgetting about rulers altogether, Charles Muller translates, "From great antiquity forth they have known and possessed it" [op.cit., Barnes and Noble Classics, 2005]. He seems to think that the passage refers to the Tao, but then to get this he leaves out the negation. Indeed, the Chinese texts of the Tao Te Ching available from various sources often leave out either the character
, "below," or the character
, "not." Muller is apparently relying on there not being a negation. He also takes
to mean "have" rather than "exist," which is an alternative meaning. Unless he also leaves out
, however, or is simply translating it as "they," he misses the point that "below" contrasts with "above," which is taken by other translators to mean the "subjects" as contrasted with the ruler who is "above." The expression 
, according to Mathews' Chinese Dictionary, can mean "heaven" or "a title of respect" [p.862]. "Heaven" would not be the same as the Tao, as Muller might be thinking (as an alternative to "great antiquity"), and the "title of respect" is what implies that this is a ruler. While D.C. Lau has a charming expression that the ruler is "but a shadowy presence," if the text says that the subjects don't even know that he exists, this hardly needs such embellishment. Similarly, while Lau ends the sequence that the ruler will be one "with whom they take liberties," the blunt statement that the subjects will insult him again hardly seems in need of an alternative expression. Another curious variation in the text occurs in Paul Carus [Open Court, 1974], who has
instead of
in the middle of "love and praise" [p.34]. This doesn't affect his translation very much [p.84], but it does otherwise seem awkward in the structure of the passage.
you ordinarily don't notice or appreciate how healthy you are until you get sick. Then you talk about health. Talking, however, doesn't bring it back. Similarly with the moral qualities. It is significant that "benevolence and rectitude" (rén and yì) are the two principal virtues of Confucius. Talking about benevolence and rectitude is what Confucius actually did. The Taoist critique is that the talking doesn't help. Indeed, talking about it really will prevent the Tao from restoring the real things. The tip-off is then that the appearance of "cleverness" or "intelligence" and "knowledge" or "wisdom" result in "great hypocrisy." Manifest qualities that should be good instead produce misuse. The Sage, with genuine intelligence and wisdom, is not noticed.
Also, "When cleverness emerges, There is great hypocrisy." This is something else: Taoism wants a simple, rural life. It doesn't like "cleverness" or "novelties." It is hard to imagine the Taoist sage in a city -- he is usually to be imagined as a hermit or wanderer in the forest (
), mountains (
), or countryside, often only uttering paradoxical statements. We see this in the character
, "an immortal," which contains the character for "mountain" with the radical for "person,"
. The idea seems to be that immortal beings live in the mountains, either because that is where the divine belong (as on Mt. Olympus) or because that it where Taoist adepts, who achieve immortality, practice their asceticism (as with Japanese practicing "mountain asceticism" in proximity to the kami). Thus, Taoists themselves can be called 
, the "immortal-ists" or "school of the immortals." The Confucian sage, on the other hand, is intrinsically urban, and most easily imagined actually in a Chinese judge's robes (like the Chinese god
, whose name can mean "success" or "official salary"). "Immortal," however, can be contrasted with
, "common, vulgar, worldly." This contains the "valley" character (
) with the radical for "person." What is down in the valley is then common, mundane, and vulgar.
"When the six relations are at variance, There are filial children." This isn't exactly what it says in Chinese. When the Six Relations are not in
, "harmony" (wa in Japanese), then what exists is filial piety (
) and affection. As we have been seeing, when filial piety and affection are not actually observed, then we talk about, and prevent there being, these filial qualities. D.C. Lau says "children," but this gives us too narrow a focus.
"When the state is benighted, There are loyal ministers." Note that Lau's "loyal" here is chung,
, which could be better translated "conscientious." "Loyal" ends up the exclusive meaning in Japanese (chû),
which unfortunately comes to mean blind loyalty and obedience, contrary to the principles of either Confucianism or Taoism. As above, when the state is in bad shape (where we literally get "darkness" and "disorder"), then we talk about, because there aren't any, conscientious ministers.
The expression here variously translated as "state," "country," or "nation," 
, is of interest in its own right. The binome adds to the character
, which already means "state" or "country" (koku or kuni in Japanese). the character
, which can actually mean "family," as well as a member of a school or organization. So, however we look at it, "nation" may be a better translation when it implies the people who are the citizens or subjects of the state. The country and its people.
Note here that the Taoist critique apparently presupposes the moral reality of the Six Relations, which includes that of conscientious ministers, and thus accepts, in its own way, this feature of Confucian ethics. With Taoist recluses wandering around and shunning ordinary society, we might take the Taoists to be anarchists; but there is no indication in Taoist doctrine or lore that such is the case. The hermits who occasionally offer their services to rulers, like Kung-ming (Kongming) below, are the exception that prove the rule: Taoism values an orderly society and a strong state.
Best illustrated by a Zen story about the Japanese monk Hakuin, who was accused of getting a neighborhood girl pregnant. She didn't want to name the real father and so accused Hakuin instead. He neither admitted nor denied being the father, only saying, "Is that so?" calmly accepting the care of the baby when it was born, even though by then he had lost his reputation. A year later the girl named the real father to her parents. Hakuin expressed no more surprise or concern over the apologies as he had over the accusations, and calmly returned the child when asked, again only saying, "Is that so?" This was the "role of the disgraced" in the most literal sense. [Paul Reps, Zen Flesh, Zen Bones, Anchor Books, pp. 7-8].
"The uncarved block." Since nothing has been done to an uncarved block, it is symbolic of the Tao.
] and weak [
] will overcome the hard and strong." The "role of the female" is made more specific: "Submissive" (jou in Wade-Giles and róu in Pinyin) is a significant, evocative term. The dictionary definition of róu (Mathews' Chinese-English Dictionary, Harvard, 1972) is "soft, pliant; yielding, gentle; to overcome by kindness." "Submissive" in Taoism, however, is not always what it might seem. We have all seen the Japanese pronunciation of róu in the word judo (
), the "Submissive Way." But Judo really doesn't look very "submissive": throwing people to the mat isn't exactly "to overcome by kindness." As a form of Not Doing, however, the idea in Judo is not to originate an attack and not to use one's own strength: the strength of an attacker is turned against him. This idea was often articulated in the old "Kung Fu" television series of the 70's, with David Carradine.
The text has "name," not "act." A similar statement, however, with "act," is below at 48:108. "The myriad creatures will be transformed of their own accord....The nameless uncarved block/Is but freedom from desire." Notice the similarity with the teaching of the Bhagavad Gita. The gunas were all forms of desire, and liberation was therefore freedom from desire. But freedom from desire in the Gita is the means to avoid rebirth, while freedom from desire in the Tao Te Ching is the means of liberating the Tao, which provides all the things that we might otherwise have desired anyway. A very great difference between world-denying India and world-affirming China.

]," doesn't talk about virtue, and so actually practices it. "A man of the lowest virtue [
]," makes a big show and a big noise about virtue, and so is most likely a hypocrite who doesn't actually practice it. Compare to Jesus's complaints about those who only give alms publicly (Matthew 6:2) or stand on the street corners praying (Matthew 6:5). "A man of the highest benevolence [
] acts..." The beginning of an implicit critique of Confucianism. Rén is the highest virtue for Confucius. Taoism doesn't have too much of a problem with that. Ames and Hall, responsible for a strange translation involving
in chapter V, give us the translation, "Persons who are most authoritative (ren) do things coercively..." Here they avoid the obvious meaning of
again and translate the word, which has so simple a literal meaning, as "authoritative," which is absurdly far off the semantic reservation. They apparently cannot tolerate the idea that Taoism might, even indirectly, endorse a Confucian virtue. They also translate
, which simply means "do," as "do things coercively," which is absurd -- but of a piece with a desire to reach for non-existence negative meanings. "A man of the highest rectitude [
, righteousness] acts, but from ulterior motive." Righteousness (yì) is the next highest Confucian virtue, but Taoism suspects those who invoke it of pursuing some self-interest. "A man most conversant in the rites [
, propriety, etiquette, good manners] acts, but when no one responds rolls up his sleeves and resorts to persuasion by force." Good manners (li3) is the next Confucian virtue, but Taoism expects nothing but intolerance and violence from people who talk about this. This is similar to attitudes in the 60's, when people felt that "good manners" were superficial nonsense and the preferred "counter-culture" behavior was rude and crude. This was not too good; but now, when certain kinds of rude behavior or speech can be prosecuted as federal civil rights offenses ("hostile environment" interpretations of anti-discrimination law), the Confucian opposite feared by Taoism seems to have been reached. "Hence when the way [
] was lost there was virtue [
]; when virtue was lost there was benevolence [
]; when benevolence was lost there was rectitude [righteousness,
]; when rectitude was lost there were the rites [manners,
]./The rites are the wearing thin of loyalty [conscientiousness,
] and good faith [
]/And the beginning of disorder [
, Japanese ran -- used as the title of Akira Kurosawa's 1985 Japanese movie version of King Lear]." A nice hierarchical listing and evaluation of moral terminology according to Taoism.
Although the stereotype of the Taoist Sage is an asocial recluse, wanderer, and hermit, there is nevertheless the tradition that such a person may nevertheless turn out to be the wisest in practical, including military, matters. A striking example of this is in The Romance of the Three Kingdoms, 


, where Liu Pei (Liu Bei), who would become the first Emperor of the Shu Han dynasty, seeks out the Taoist recluse Chu-ke Liang (Zhuge Liang), known as Kung-ming (Kongming). Liu Pei travels three times to find Kung-ming before obtaining his services. Then Kung-ming serves the Dynasty with superior administrative, diplomatic, strategic, and tactical abilities. Thus, while the prevalent political ideas of classical China are Confucian, there is the suspicion that the Taoists may actually know more about the way things work -- including magical abilities, which Kung-ming also uses occasionally.
Verse 108: "...and when one does nothing at all there is nothing that is undone." The essential paradox of Taoism, but it also gives away the trick. Things do get done.
, "The more taboos..."
is an interesting expression. It can mean, "to shun the use of sacred names; to avoid things taboo; superstitious avoidance of things; taboo; prohibitions." The question then might be whether the Tao Te Ching means specifically religious prohibitions, or legal prohibitions in general. Or perhaps both. "The more sharpened tools..." The phrase here is 
, where
is "profit, gain, advantage," or "sharp, cutting; witty," and
means, "vessel, utensil, implement, instrument" (see the use of this by Confucius). The expression can mean "edged tools" or "cutlery," or the meaning may be more metaphorical. Either "sharp" can mean mentally so, or we could take the primary meaning of lì and say "profitable tools." The statement thus could be about the fear of violence from weapons, or it could imply the general Taoist fear of novelty and wealth from productive technology. An ambiguity would be characteristic of Taoism. "The further novelties multiply": Again, Taoism wants a simple, rural life. "The better known the laws the edicts/The more thieves and robbers there are." Taoism is not going to care much for laws (
), and it is certainly true that the multiplication of laws in effect creates more crime. The prisons today are full of people who have broken laws (mainly drug laws) that simply didn't exist a hundred years ago, while a great deal of litigation is about issues (e.g. over discrimination) that would have been considered private matters even seventy years ago.
Verse 133: "I am not meddlesome and the people prosper of themselves." This line can also be translated [third line at right], "I do not serve, and the people themselves become wealthy." For discussion of
as meaning "to serve," see the treatment at Analects VI:28. This principle suggests the "Tao of capitalism," since the principle of the free market is to leave people alone (laissez-faire), by which the "Invisible Hand" of Adam Smith (the Tao) will be able to create wealth for everyone. Such a result would not necessarily be what Taoism had in mind: "I am free from desire and the people of themselves become simple [like the uncarved block]" [fourth line at right]; but a free market economy, by created unprecedented wealth, does just the opposite. Taoism wanted a simple, rural life, without "cleverness" or "novelties," but leaving people alone to become wealthy means that they will -- which produces a vast consumer market of "cleverness" and "novelties" far from simplicity.
] overcomes the hard [
]." The character here for "hard" we find in
, the term for the vajra, the thunderbolt of Indra, the symbol of power in Vajrayana Buddhism, and the name of the Japanese battleship Kongô. Even Taoist war, of course, is indirect and undermining, not hard and frontal -- as, again, we see in The Romance of the Three Kingdoms.
], would simply disappear in the Taoist ideal.

Zen and the Art of Divebombing, or The Dark Side of the Tao
History of Philosophy, Chinese Philosophy
Sun Tzu sounds the most like a Taoist when he counsels against frontal attacks. One should direct one's army as though it were the supreme example of the Tao, water, One of the most important pieces of advice in Sun Tzu is stated very briefly: 圍師 遺闕, Wéishī yíquè [literally: "surround army, leave hiatus"], "When you surround an army leave an outlet free" [The Art of War, Bilingual Chinese and English Text, 7:36, Sun Tzu, translated by Lionel Giles, Tuttle, 2016, p.31; De Re Militari, translated by Lionel Giles, edited by Lieutenant John Clarke, Roots of Strategy, The 5 Greatest Military Classics of All Time, edited by Brig. Gen. Thomas R. Phillips, 1940, Stackpole Books, 1985, p.40], or "[B]e sure to leave an opening for an army that is surrounded" [Victor H. Mair, The Art of the War, Sun Zi's Military Methods, Columbia University Press, 2007, p.104].
Sun Tzu does not explain why one should leave an opening. The effect of it, however, we can see in the Battle of the River Sajó (or Mohi), fought by the Mongols under the Khân Batu against King Bela IV of Hungary in 1241. After some Hungarian success, the Mongols surrounded the Hungarian camp. Leaving a gap in their encirclement, the Mongols tempted the Hungarians to flee, which they did, and could then be cut down on the run.
Where we find an explanation of this practice is in the Roman strategist Flavius Vegetius Renatus [De Re Militari, Roots of Strategy, The 5 Greatest Military Classics of All Time, op.cit., pp.65-175]):
Nothing could so vividly describe the result of an action like that of the River Sajó. The reference of the "golden bridge," however, has not always been understood in military history. Thus, the Marshal Maurice de Saxe of France (1696-1750) in his "My Reveries Upon the Art of War" says:
De Saxe apparently is thinking that the "bridge of gold" means that one should allow the enemy to escape. He cannot have recently read Vegetius if he believed such a thing. But he is clearly aware that a retreating enemy can well provide an opportunity for attack. He does not express, however, as Vegetius does, under what circumstances a retreating enemy can be fruitfully attacked.
We return to Sun Tzu again, who says, 佯北 勿從, Yángběi wùcóng [literally: "pretend defeated, don't go after"; 北 usually means "north," which confuses automatic translations], "Do not pursue an enemy who simulates flight" [Tuttle, op.cit., 7:34, p.31; Lionel Giles, op.cit., p.40]. An orderly retreat may be as difficult to attack as a resolute defense. Vegetius sees opportunity when the retreat of the enemy is a flight in panic, which can be induced by providing the "bridge of gold" to an army already demoralized.
We must always guard, however, against deception by an enemy who wants us to think that they are fleeing in panic. This was how the Arabs often defeated their enemies; and we see the same tactic used decisively by the Turks at the Battle of Manzikert in 1071, delivering Anatolia to Turkish invasion and migration. The Turks gave way and appeared to flee, but then they turned on the pursuing Romans, who had become disorganized in their own enthusiasm. The Emperor Romanus suddenly understood his peril, but his orders then, at least, further confused his army. In more subtle fashion, Hannibal had given way before the Romans at Cannae, to lure them into a pocket, where they were slaughtered.
The Taoist way of war is thus not so unique after all, and it even clarifies the value of Sun Tzu's advice when we compare it with strategists in Western military history. We might say that Vegetius does a much better job of explaining Sun Tzu than Sun Tzu does.
Philosophy of History, Military History

Comments on the Tao Te Ching, Note;
Sun Tzu and Flavius Vegetius Renatus
. Water overcomes obstacles by flowing around and undermining them. The ideal battle for Sun Tzu is won before action is even joined.
THE FLIGHT OF AN ENEMY SHOULD NOT BE PREVENTED, BUT FACILITATED. Generals unskilled in war think a victory incomplete unless the enemy are so straightened in their ground or so entirely surrounded by numbers as to have no possibility of escape. But in such situations, where no hopes remain, fear itself will arm an enemy and despair inspires courage. When men find they must inevitably perish, they willingly resolve to die with their comrades and with their arms in their hands. The maxim of Scipio, that a golden bridge should be made for a flying enemy, has much been commended. For when they have free room to escape they think of nothing but how to save themselves by flight, and the confusion becoming general, great numbers are cut to pieces. The pursuers can be in no danger when the vanquished have thrown away their arms for greater haste. In this case the greater the number of the flying army, the greater the slaughter. [p.164, boldface added]
The words of the proverb: "A bridge of gold should be made for the enemy," is followed religiously. This is false. On the contrary, the pursuit should be pushed to the limit. And the retreat which had appeared such a satisfactory solution will be turned into a route [sic]. A detachment of ten thousand men can destroy an army of one hundred thousand in flight. Nothing inspires so much terror or occasions so much damage, for everything is lost. [Brig. Gen. Thomas R. Phillips, op.cit., p.299]