Where it gets tricky is that it can be hard to see from the outside whether a system continues to do B because they don’t care about B, because it’s impossible hard to do A without also doing B, or because they are trying really hard to avoid doing B but haven’t really worked out how yet.
Looking at what a system rewards lets you see which of these situations the system is actually in. If they are actively rewarding people for not doing B, then B is not the purpose of the system.
One interesting subtlety is what we should say about a system whose purpose is A, that rewards A, and yet ends up doing a lot of B. I think that B isn’t the purpose unless it actively rewards B, but you could say the purpose is to “do A, and tolerate doing B in course of doing A”.
There is definitely some truth in what you say.
Where it gets tricky is that it can be hard to see from the outside whether a system continues to do B because they don’t care about B, because it’s impossible hard to do A without also doing B, or because they are trying really hard to avoid doing B but haven’t really worked out how yet.
Looking at what a system rewards lets you see which of these situations the system is actually in. If they are actively rewarding people for not doing B, then B is not the purpose of the system.
One interesting subtlety is what we should say about a system whose purpose is A, that rewards A, and yet ends up doing a lot of B. I think that B isn’t the purpose unless it actively rewards B, but you could say the purpose is to “do A, and tolerate doing B in course of doing A”.