If you reread my comment, you will see that I never said the purpose was what it does.

That word choice was not by accident, it wasn't meant to be a simple paraphrase.

I said a system is what it does. In this case bars are the cause of drunk driving, just like in my parallel. Not on purpose. But by effect.

You mismatched my statement to the famous quote, then pointed out it didn't fit. I know that one doesn't. That's why I said something different.

My entire point is that identity and effect are not the same as purpose.