That's fair, but you're talking about conscious justification in technical economic papers. We're not necessarily the best judges of why we do what we do, as Freud showed (because our decisions can be unconscious, intuitive, emotional, and otherwise nonrational).

So I'm talking about the overall support for capitalism that comes from mainstream economics. And my question is what kind of rationality you need to assume to support capitalism as a way of maximizing utility. I'm arguing that egoism is one thing, and instrumental rationality (the optimizing of means to achieve open-ended ends) is another. And they don't work equally well in an evolutionary defense of capitalism as a self-regulating system.

Hence the equivocation I'd expect to arise. Call this a hypothesis. No, I haven't done a dissertation to comb through the literature to prove the hypothesis is correct. Luckily for me, labour can be divided.

Also, it's interesting that you translate the invisible hand argument into that particular model. Isn't it possible that economists, like everyone else, can be motivated by philosophical assumptions and even prejudices? Isn't it possible that some Darwinian line of reasoning, like the invisible hand argument, might unconsciously tilt the whole mainstream economic celebration of capitalism?

Just because we don't explicitly avow something, doesn't mean we don't really believe it. There can be all kinds of reasons why we'd rather present ourselves in the best light, and have a misleading self-image.