權衡價值的方法（上）

　　辯論比賽的題目必須具有「可辯性」，意思就是說正反雙方都立場，肯定都有其道理，否則我們沒必要也沒辦法進行辯論。

　　面對兩個衝突的價值，該怎麼樣選擇，就是我們要處理的課題。

　　1945年心理學家鄧克(Duncker)曾經提出一個兩難的問題，又被稱為鄧克輻射難題，他說有個病人得了癌症，他太虛弱不能動手術，只能使用放射線治療。可是如果放射線太強可能會傷害到健康的組織，放射線太弱，又無法完全消滅癌細胞，那麼究竟該不該使用放射性治療呢？

　　針對這個兩難的問題，另外兩個心理學家吉克(Gick)和霍約克(Holyoak)給了我們一個故事作為提示：

　　A small country was ruled from a strong fortress by a dictator. The fortress was situated in the middle of the country, surrounded by farms and villages. Many roads led to the fortress through the countryside.

　　A rebel general vowed to capture the fortress. The general knew that an attack by his entire army would capture the fortress. He gathered his army at the head of one of the roads, ready to launch a full-scale direct attack.

　　However, the general then learned that the dictator had planted mines on each of the roads. The mines were set so that small bodies of men could pass over them safely, since the dictator needed to move his troops and workers to and from the fortress. However, any large force would detonate the mines. Not only would this blow up the road, but it would also destroy many neighbouring villages. 　　It therefore seemed impossible to capture the fortress.

　　However, the general devised a simple plan. He divided his army into small groups and dispatched each group to the head of a different road. When all was ready he gave the signal and each group marched down a different road. Each group continued down its road to the fortress so that the entire army arrived together at the fortress at the same time. In this way, the general captured the fortress and overthrew the dictator.

　　故事大概是這個樣子，有個小國被一個住在要塞的獨裁者統治，要塞位在國家的中央，周圍環繞著許多小村莊，因此有許多條路通往這個要塞，為了避免遭到大規模進攻，獨裁者在村莊通往要塞的每條路上都埋滿了地雷，這個地雷被設定成只能允許小規模的人員移動，否則就會爆炸。

　　有一天，反叛軍決定進攻獨裁者所在的要塞推翻政權。為了避免太多人同時行動引爆地雷，叛軍的領袖決定分批行動，然後在各個部隊抵達時，發出信號同時進攻，最後終於攻下了要塞。

　　看完了這個故事，我們知道只要把放射線分開使用，這樣既不會破壞健康組織，又可以消滅癌細胞，問題於是迎刃而解，皆大歡喜。

　　不過我們進一步分析這個問題，會發現真正衝突的部分其實沒有被解決。

　　我們仍然沒有辦法同時使用強的放射線治療和弱的放射性治療，也沒有辦法又是分頭行動又是集中行動，解決問題的方法其實是：「找出對方背後的價值（前提）」

　　使用強的放射線，和集中行動的理由，都不僅僅只是醫生「想要」用強的放射線或者叛軍領袖「想要」集中行動，而是它們背後的利益，那才是真正重要的東西。

　　現實中，許多正反的意見都只是當下的衝突，只要把稍微轉換一下視角，我們就會發現全新的世界，哲學上我們稱呼其為「辯證法」。

　　然而要怎麼樣才能知道，什麼才是真正重要的東西呢？

　　我們下一篇再談。