William Broadway, a student at Loughborough University, has invented a way of keeping vaccines cool which might save over a million lives by reviving an invention of Albert Einstein's. This reminds us of an important fact - that intellectual progress isn't necessarily linear. Instead, good ideas can be forgotten and bad ones developed, so that science can regress.

For example, the Romans knew how to remove cataracts, knowledge which wasn't rediscovered until the 20^th century; the steam engine was invented in the first century AD, but long forgotten; and the standard of battlefield medicine might well have been higher in the British civil wars than it was at Crimea two centuries later. The renaissance was so-called because forgotten knowledge was rediscovered.

What's more, a lot of what looks like progress ain't so. The replications crises in psychology, economics and medicine (if such there be) warn us that new findings aren't wholly reliable.

I don't say this to come over all John Gray on you and deny the existence of progress. Instead, I do so to challenge an implicit presumption many of us have - that today's work is superior to that of 10, 20 or even 100 years ago.

Instead, it's possible that peer review and grant-awarding processes sometimes select for fashionable rather than effective research; that informational overload means that some good ideas get neglected; and/or that increasingly narrow fields of specialism cause inspiring ideas from separate fields to be ignored.

It's from this perspective that we should view the debate about the relative merits of stock-flow consistent or heterodox models against DSGE ones. I don't want to take a view on Brad DeLong's claim that DSGE models have been "a catastrophic failure", but I can say that if they are there's nothing unique about fashionable research programmes being a dead-end or in once-forgotten ideas proving powerful when they are revived.

To take but two examples of the latter, I'd suggest that the macroeconomics of income distribution are better analysed through Marxian-Kaleckian (pdf) models in which power matters rather than through more "modern" theories, and that the theory of natural selection - which Darwin took from economics - contains many insights that enrich our understanding of economics.

My point here should be a trivial one. We should not presume that newer means better, because institutions don't always select ideas optimally. One reason why we should study the history of ideas is that doing so reminds us of this fact.