Water and sudden assault

Introduction

Two very short chapters this week, Defense Against Water and Defense Against Sudden Attack, answering "water" and "sudden assault" among the twelve methods.

"Water" means diverting a river to flood the city. Defense Against Water says the city must dig in advance a ring road and channels along the inside of the wall, "eight paces wide," for drainage; when the water comes, cut channels inside to lead it away, and at the same time lash boats together into "ten units" of thirty men each, using deck-boats to carry crossbowmen out over the water to break the enemy's dams. The logic is plain: water is the enemy's weapon and also his weakness; break the dam and it floods him instead.

"Sudden assault" is a rush on the gate. Defense Against Sudden Attack is ingenious: every hundred paces a "sally gate," and behind it a kiln-oven whose mouth opens into the gate passage, stocked in advance with mugwort and other things that smoke. When attackers rush the passage, drop a wheel from above to block it, then work the bellows (橐) and drive the smoke in. No hand-to-hand fighting; the smoke pushes them out.

Notice three things. First, everything is done beforehand: channels dug, boats built, ovens laid. A sudden assault is dangerous precisely because it gives no time to prepare, so preparation must be finished before it comes. Second, everything is testable: water runs downhill, smoke rises, and the Mohists' grip on such regularities came from repeated observation, of a piece with the optics in the Canons. Third, everything kills as few as possible: smoke, a blocked gate, a broken dam. The aim is to make the attack fail, not to destroy the attackers. This is what non-aggression looks like from inside a besieged city.

The three tests

Both chapters stand on the second test, but this "checking" differs from the checking in Explaining Accountability. There, crowds "saw the forms of spirits and heard their voices," and the argument rests on the number of reports. Here it rests on repeatable observation: dig the channel and the water goes; work the bellows and the smoke goes in. This week, separate the two kinds of "what people see and hear": "many people say so" versus "anyone who tries it gets the same result." 墨门 / The Mohist Community holds that only the second kind passes the second test.

For families

• 科技堂: in a tray of sand, build a city and a dam, then pour water to try "cutting a channel." Where must the ditch go for the water to bypass the city?
• 科技堂: with an adult present, watch where smoke from a candle goes through a paper tube, and discuss why the bellows blow from below.
• Decide the household's "first step": what to do first in a fire, first in a flood, and write it down.

For chapters

• 20 min reading · 20 min 墨辩 · 10 min 三表 review · 10 min 职 reports.
• 墨辩 motion: "A defense should aim for the fewest casualties even at greater risk to the defenders." One side cites the smoke oven; the other argues from the defenders' duty to the people inside.
• 三表 review: give one example each of "many say so" and "anyone gets the same result," and ask which kind the chapter's most recent decision relied on.