Economist Alex Tabarrok (GMU) recently wrote of “ideas behind their time”.

He explains:

We are all familiar with ideas said to be ahead of their time, Babbage’s analytical engine and da Vinci’s helicopter are classic examples. We are also familiar with ideas “of their time,” ideas that were “in the air” and thus were often simultaneously discovered such as the telephone, calculus, evolution, and color photography. What is less commented on is the third possibility, ideas that could have been discovered much earlier but which were not, ideas behind their time.

Tabarrok’s post is mainly about physical inventions, and someone’s attempt to use AI to come up with a list of such inventions that appeared “behind their time”.

The results?

Most useful technologies tend to be invented quite quickly once they are possible—this is reassuring. The airplane, for example, could not have been invented before a high power-to-weight engine, which happened circa 1880 making the late 1880s the earliest feasible date for powered flight. Thus, the Wright Brothers (1903) were only just behind the earliest feasible date—and that is true for many inventions. The ideas very far behind their time include the stethoscope, general anesthesia and reinforced concrete and quite far behind are the Jacquard loom and canning.

The post made me wonder about philosophical ideas behind their time.

One might think that nearly all but the very earliest philosophical ideas are behind their time, in that it is possible that they could have been thought up by sufficiently smart and creative persons at any point in history. While the light bulb could not have come into existence prior to developments in glass blowing, metallurgy, and the control of electricity, philosophical thoughts aren’t like that. Anyone could have thought up “act so that the maxim of your act could be willed as a universal law” at any time.

But that response seems to misunderstand what the query about philosophical ideas behind their time is about. It’s not a question about logical or metaphysical possibility. Rather it’s a question about likelihood, about what it is reasonable to expect from particular types of persons in particular cultures at particular times.

Of course “reasonable to expect” is ambiguous.

And there are other relevant ambiguities, too, regarding the identity of ideas and the kinds of ideas the inquiry is about.

For example, it seems true that “a solution to the mere addition paradox” could only be offered after Parfit introduced the paradox in the 1980s (here’s one presentation of it). So if the “solution” showed up in, say, 1990, it doesn’t seem behind its time. But what if the solution is just the application of an idea that it wouldn’t have been unreasonable to expect someone to have conceived of 100 years earlier? Perhaps under one description, as a solution to the paradox, it is not behind its time, while under another a different description, as the insight that is brought to bear on the paradox, it is? And if it’s not the application of a more general idea, perhaps it is too narrow a case to be sufficiently interesting?

I don’t have answers to these questions. I just raise them to acknowledge that the inquiry itself is a bit fuzzy.

That said, it might be best to proceed by offering examples and seeing how satisfactory we find them.

Here’s one: Gettier problems. Gettier presented these in 1963. Arguably, though, they were invented by Bertrand Russell in 1948 [though see the first comment, below]. Early formulations of the conception of knowledge as justified true belief which these problems target go back to Plato. Gettier cases do not seem to rely on any conceptual, methodological, technical, or empirical achievements made over the past two millennia. So should we conclude that Gettier cases are about 2300 years behind their time?

I’m neither an epistemologist nor a historian of philosophy, so if I’ve made some error with the above example, please let me know.

But if the example is a good one, there is another question that we might benefit from looking into: why did it take so long for Gettier-style problems to arrive on the scene? More generally: what are the obstacles to philosophical progress?

UPDATE (5/15/26): Tabarrok posts at Marginal Revolution about this post, offering some of his own suggestions for philosophical ideas behind their time, including the is/ought distinction, the problem of induction, the acts/omission distinction, religious toleration, the analytic/synthetic distinction, and others.