Jonathan Catalan tells me that "all purposeful action is market action".
This strikes me as absurd. All market action is certainly purposeful action, I'll agree - and understanding human pursuit of purpose is clearly going to help you understand market action. But there is a lot of purposeful action that is not market action at all.
Economics ought to restrict itself to market action in my opinion. Psychology has done well as a science of the mental and behavioral processes underlying all human action, and thus has a lot of good things to say to any scientist considering the human species. Economics has done well as a science of market action. Sociology and political science, despite a few gems, have faltered in important ways, so you see economists doing reasonably good work in both fields ("economics of the family", etc. for sociology - public choice theory for political science). We have good tools that any science of these types of action ought to consider using (and in many cases they have), but ultimately this is niche-filling.
But the fact that economic scientists have transferable skills that can fill these niches doesn't make these other purposeful actions "market actions". Market action is action in the context of networks of transactions. Not networks of interactions (that's sociology). Not networks of domination (that's political science when it is state domination, sociology otherwise). But networks of transactions. That is market action, and it's important not to fool ourselves into thinking that we're experts in more than what we are experts in. I know bits and pieces about the science of human domination of other humans, or the science of human non-market interactions with other humans. But mostly I know about market action.
Anyway - I thought this would be a fruitful comment thread. Why on Earth would anyone think that all purposeful action is market action? What exactly does "market" mean if that's the case?