don't have to worry about externalities,

你无须担心外部效应
and yes you have to worry about perfect competition but once

但你要担心完全竞争市场
you've got perfect competition that's the end of the story.

一旦你面对完全竞争故事也就结束了
So the rest of the course now is going to be,

那么剩下的课程将会是
if you forget about externalities because you forget

由于我们交易的是没有污染的纸
about pollution because we're trading pieces of paper,

那么我们就会忘记外部效应
they're not polluting anything,

因为它们不会引发污染
why shouldn't the financial markets be efficient?

那为何金融市场不是有效的呢
Why doesn't this argument apply to the financial markets,

为何这个论证无法用于金融市场
and one of the critical financial markets is the credit market.

金融市场的一个重要部分就是信贷市场
So can you understand the credit market on just these

那么基于信贷市场你能理解
terms and therefore argue that the market's efficient?

刚才那些用于争论市场有效性的理论么