[finghin]

I also agree that Marx is a thinker who altered the course of the world and I see where you are coming from regarding the moral judgement on his absence.

As a counterpoint, what would Marx’s great intellectual achievement be, and could it stand up to the early capitalists like Smith?

What comes to mind is the Labour Theory of Value, and I would say it is a strong candidate for sure. Whether it figures as a key human intellectual achievement is definitely at best borderline compared to the other exemplars on this list.

[bazoom42]

The idea that history is driven by material conditions.

[aerhardt]

I would say historical materialism is way more influential. His theory of value was quickly dispelled (although many continued to believe in it) but all marxist and post-marxist thinkers (the Frankfurt school, French post-modernists, current woke academicians) continue to use historical materialism in one way or another.

[finghin]

Good point, and noted