[notahacker]

I'm unfamiliar with Blatt's book (sounds interesting) but assumptions about humans attempting to predict the future don't really get any simpler than human misjudgements of the future don't follow a pattern an economist can predict (and to a lesser extent, companies try to make more profit where possible is also a pretty weak assumption). Especially when the whole reason this came to be popular was the analytical tearing apart of theories which used reasonable sounding alternatives people will base their expectations on what happened last time by pointing out that some people - even a minority - would make enormous amounts of money if chose to behave differently from how the economist said people would would behave, or that "I would like my wages to be the same as last year" would be a really stupid thing for workers to bargain for if the government has stated they're trying to boost the economy by purposely creating inflation. The other side of that argument is there are some conclusions drawn from some rational expectations models which are a bit too dependent on the assumption that people [on average] won't make prediction errors at all.

I've got plenty of time for the post-Keynesians but most of them (particularly in the Keen Godley/Lavoie Social Accounting Matrix style) really aren't doing more complicated mathematics so much as choosing to have models far more sensitive to specified lag structures and/or using different assumptions about human behaviour (The flip side is that Keen's hypersensitive-to-how-it's-specified banking system is better in many respects than a macro model with no banking system or credit constraints) For much of the last century the Cambridge post Keynesians distinguished themselves by doing a lot less modelling than their neoclassical counterparts.