如此简单的道理他都不懂 英语怎么说?

楼上什么乱翻译，第三人称都不知道？

He doesn't even know such an obvious fact.
fact可替换为其他同义词
principle也可，不过太书面

He doesn't know such a simple reason actually !

he even do not know such simple principle

He doesn't even know such a simple thing.