And yes, there is a paradox here. The class Class is an instance of itself; that is, it’s a Class object. And there’s more. Remember the class Object? Well, Object is a class … but classes are objects. So Object is an object. And Class is a class. And Object is a class, and Class is an object.
Which came first? How can the class Class be created unless the class Object
already exists? But how can there be a class Object (or any other class) until there’s a class Class of which there can be instances?

绕口令。。。

Class和Object是蛋跟鸡？

就跟摆摊用铝冶锅的锅模子跟冶出来的锅一样，是不是可以这么形容一下子