Towers and ladders

Introduction

Two short chapters this week: Defense Against High Approaches and Defense Against Ladders.

A "high approach" is an earthen platform (羊黔) piled up outside the city, higher than the wall, to shoot down into it. Mozi's answer is the multiple-bolt crossbow cart (连弩之车), a large crossbow mounted on the wall, firing several long bolts at once with cords on their tails so they can be winched back. It is the most concrete machine in the Mozi. The idea: the enemy relies on height, we rely on range and density of fire; do not compete for height, make the platform impossible to stand on.

Defense Against Ladders opens with a story. Qin Guli followed Mozi for three years, hands and feet calloused, face burnt dark, doing menial work, not daring to ask for what he wanted to learn. Mozi, moved, prepared wine and dried meat, made an offering on Mount Tai, seated him and poured for him. Qin Guli bowed twice and sighed, and only then asked: how do we defend against cloud ladders? Mozi answers: build a "moving wall" (行城), a temporary work "twenty feet above the wall," with battlements; set side towers to cover each other; hang fire (悬火) down to burn the ladders; send picked men out through the side gates, moving to the drum on the wall.

This story carries special weight in 墨门 / The Mohist Community. It is about lineage (学脉): skill is not handed over casually; it goes to those willing to work first. But it raises this week's question. Three years without asking: respect, or waste? Mozi speaks first in the end, which suggests he too felt it had gone on too long.

The three tests

Both chapters' devices rest on the third test, whether they work, and the evidence that they work comes from actual sieges (second test, what defenders saw with their own eyes). Qin Guli's story concerns the first test: how lineage is passed on is a precedent. The Community keeps the "serve first, then ask" tradition but shortens the three years to one service cycle and requires the chapter lead to ask first. Nobody willing to learn should wait three years. That change was made by the test of use.

For families

• 科技堂: build a "multiple-bolt crossbow" from rubber bands, lolly sticks and a clothes peg, compare ranges, and discuss why a cord on the bolt is useful.
• Tell Qin Guli's story and ask the children whether there is something they badly want to learn but have not dared to ask. Ask it this week.
• Build a "moving wall" from chairs and blankets and discuss why a temporary raise is faster than rebuilding the whole wall.

For chapters

• 20 min reading · 20 min 墨辩 · 10 min 三表 review · 10 min 职 reports.
• 墨辩 motion: "Lineage should require service before teaching." One side cites Defense Against Ladders; the other argues from impartial care and honoring the worthy.
• 三表 review: does the chapter have anything only one person knows how to do (accounts, website, keys)? On the crossbow-cart principle, name a backup for each.