In this article no in-depth explanation of Chinese characters, hardly references, just an interesting story. There is a fascinating link with hexagram 29 and a passage from the Mozi 墨子. The name of this hexagram, kan 坎, means 'pit, hole in the ground, trap'. But used doubled (kan-kan 坎坎) it is an onomatopoeia for the sound of drumming, as in the poem Fa Tan 伐檀 in The Book of Odes:
坎坎伐檀兮 Kan-kan go his blows on the sandal trees...
Often when a character is doubled it is a representation of a sound. We find this doubling in the third line of hexagram 29:
來之坎坎 The kan-kan of coming/approaching...
Something which produces a kan-kan sound is approaching.
The trigram Water is associated with danger, and with the ears, with listening. All these elements of
sound of drumming
...can be found in a passage from the Mozi, which describes an alarm system to discover enemies who are approaching a city through underground tunnels. It can be found on p. 799 of Ian Johnston's translation.
Ralph Sawyer describes it like this:
Mo-tzu's counter-methods were premised upon intensively observing the enemy's activities from high lookout towers in order to detect any evidence of excavations, such as new earthen mounts or sudden turbidity in moat or river water. These visual efforts were to be supplemented with a virtual network of listening wells positioned every five paces around the wall's interior, excavated to a minimum depth of fifteen feet or three feet below the water line. Guards, whose task was facilitated by large earthen jars fashioned specifically for the purpose with thin leather membranes stretched over the mouths, were posted at the bottom to carefully listen for any indication of enemy tunneling. Once detected, these multiple wells would allow a fairly accurate determination of the tunnel's location preliminary to mounting countermeasures." Fire and Water - The Art of Incendiary and Aquatic Warfare in China, p. 33
The drum in a pit, listening for approaching danger - it all fits the imagery of hexagram 29 pretty well. We can even find it in the text of hexagram 29:
Judgment text: 習坎.有孚.維心亨.行有尚. Repeated kan. Inspire confidence. Protect the inner offering. To proceed is helpful.
The drums are sounding, meaning that enemies are approaching! The lord has to inspire confidence in his people and his army to defend the city. The central offering in the city has to be protected. Proceeding the enemy (as Mozi suggests) is helpful.
Line 1: 習坎.入于坎窞.凶. Repeated kan enters the pit. Ominous.
The sound that the digging soldiers produce enters the pit through the drums. Danger is coming!
Line 2: 坎有險.(求小得.) The pit has danger. (Seek small results.)
The sound the drums make signifies danger. (As an oracular omen this means only small results can be achieved.)
Line 3: 來之坎坎.險且枕.入于坎窞.勿用. The kan-kan of approaching. Danger is more and more nearing. It enters the pit, which is of no use anymore.
The enemies are getting closer, and have reached the drum pits which are close to the city. (see for 'nearing' as a meaning of 枕 the 漢語大詞典, Vol. 4, p. 880).
Line 4: 樽酒簋貳.用缶.納約自牖.(終無咎.) Wine vessels and baskets cannot be trusted. Use earthenware. Cover its opening. (In the end no fault.)
A description of the type of vessel to be used (I translate 納約 as 'to cover'
because 納 can mean 'to wear' and
約 'to tie up') and what to do with it.
Line 5: 坎不盈.祇既平.(無咎.) The kan-drum/pit is not full, the earth spirit is at peace. (No fault.)
The drums do not sound, so nothing is wrong.
I don't see how the sixth line can be linked with all this, and no doubt I am translating the texts in a direction which fits my purpose. Nevertheless I found it a very interesting connection which gives additional meaning & interpretation to hexagram 29 when you receive it as an answer from the Yi.
Was any ancient Chinese city ever attacked by digging a tunnel?
What is the evidence that this drum-in-a-pit invasion alarm was anything other than an idea? Did it ever exist? Or was it merely a proposal?
It's an interesting take on hexagram 29, but it doesn't seem at all likely to me. As an interpretation it relies on the repeated kankan in the third line, which doesn't only refer to the sound of drumming.
It is an interpretation, yes. I found it interesting that some elements of the passage from the Mozi could be found in hexagram 29, and I interpreted the text in that direction. I don't know if Chinese cities were ever attacked by digging tunnels, or if this 'invasion alarm' ever existed.
All interpretations welcome. I don't think we can know anything about the Yijing save through interpretation. I interpret the kankan of the third line as the sound of a body thudding into the pitfall trap. To me this line means there's nothing you can do. But in your interpretation presumably the invading army is detected, so how do you interpret the 'do not use'? Surely if the invader is detected this would make this line a good line rather than a line of inability to do anything? So if you get it in practical divination, how would your interpretation colour its meaning in terms of addressing a situation?
In my interpretation the danger, the invading army, is approaching, and finally it enters the pit, rendering it useless. In divination it could try to tell you that when you know that danger is approaching, even when it is still far away, you should act immediately. If you wait for the danger to approach, the tools that you use to discover or avoid that danger will be useless. When the burglar alarm goes off, don't wait for the police to come but get yourself into safety. This is not the time to take risks. In other words, the 'do not use' can mean that you should not let the situation worsen if you know that the seeds of misfortune are planted. Shovel them away immediately.
If the invading army has entered the pit where the drum alarm is then I don't see how that renders the pit useless, since its only use is to tell if an invader is coming and from what direction. You'd be quite certain by that point. Also, if one were to invade a city by digging a tunnel, you presumably wouldn't want to begin digging it too far away, so the invader would surely be visible on the surface anyway. Strikes me the best defence against tunnels is a deep moat. You don't need an alarm if there is no point digging the tunnel in the first place.