上句见：Day240
The Story of Philosophy《哲学的故事》第1章Plato第4节IV. The Ethical Problem第2段第3句：
Cephalus answers that wealth is a blessing to him chiefly because it enables him to be generous and honest and just. Socrates, after his sly fashion, asks him just what he meant by justice; and therewith lets loose the dogs of philosophic war. For nothing is so difficult as definition, nor anything so severe a test and exercise of mental clarity and skill. Socrates finds it a simple matter to destroy one after another the definitions offered him; until at last Trasymachus, less patient than the rest, breaks out "with a roar":
"What folly be possess you, Socrates? And why do you others all drop down at one another's feet in this silly way? I say that if you want to know what justice is, you should answer and not ask, and shouldn't pride yourself on refuting others…. For there are many who can ask but cannot answer"(336)
浙江大学译本： 下定义是最困难的，也是思维清晰程度和逻辑推理能力最严格的测试和练习。
解析
这句讲下定义的难的程度及下定义的作用。用for来插入说明苏格拉底追问的原因。
1、For nothing is so difficult as definition, nor anything so severe a test and exercise of mental clarity and skill.
没有什么比下定义更困难，也没有什么比下定义更能严格检验及锻炼心智的清晰度及技巧。
nothing is so … as…：是个比较结构，表示“没有比……更……”
There can be no doubt that in this world nothing is so indispensable as love.毫无疑问，在这个世界，没有什么比爱更不可或缺了。《少年维特之烦恼》
severe: requiring great effort严峻的
Would you think me impertinent if I were to put your theories to a more severe test?我现在给你一个比较复杂的考验，你不觉得我鲁莽吗？《福尔摩斯探案集之四签名》
没有什么比下定义更困难，也没有什么比下定义更能严格检验及锻炼心智的清晰度及技巧。
