[noslenwerdna]

Is the purpose of a system really what it does though? Obviously there are side effects and tradeoffs in any complex system. Is the purpose of a vaccine to make you sick - no, but that is a side effect of some vaccines on some people.

If we apply the "purpose of a system is what it does" to itself, this methodology is more a way to generate interesting (and cynical) hypotheses than to get at the truth.

[bigstrat2003]

The purpose of a system is not, by definition, what it does. It is what it is meant to do. That saying really gets under my skin because it is so obviously untrue. By the logic of the saying, the purpose of a hospital oncology floor is for their patients to die. Which is obviously ridiculous, but true under the "it's what it does" thinking.