I appreciate that learned response to Keen, although I have little way of knowing who’s right on those technical questions.

At first glance, it seems there’s a semantic issue here about the meaning of “law.” You’re saying, I think, that the law isn’t falsified because the law of demand holds in some cases, whereas Keen seems to be assuming that any single exception falsifies the law, so that the only way to sustain the law is to attribute it to the ideal world in which some crazy assumptions hold true. Of course, a ceteris paribus law necessarily has exceptions, but for that very reason, many philosophers of science have come to doubt that those regularities or probabilities conform to laws. The very notion of a law of nature is deistic and archaic.

Whether neoclassical math requires necessities rather than just probabilities because the model is supposed to be dealing with an idealized case, I don’t really know. My suspicion, though, is that these technical disputes are all beside the point and are obfuscatory.