替代的零件往往不能代用

Interchangeable parts won't.
替代的零件往往不能代用。
 

What has been will be again，what has been done will be done again；There is nothing new in the sun.
过去曾如何，未来会再是，过去曾做过的，也适必再发生；太阳底下没有新鲜的事。

Those who cannot remember the past are condemned to repeat it.
凡不能记取过去的人注定要重蹈复辙。

A theory should be as simple as possible, but no simpler.
一个理论应该尽可能简单，但不能再简单。