My favourite example of this in more recent times is this one:

Erich Fromm articulates the idea of negative liberties vs positive liberties (e.g. “the freedom from being slandered” vs “the freedom to say whatever you like”) in his Escape From Freedom/The Fear of Freedom (depending on which part of the world you’re in the title was different).

The only problem is that Fromm is a German and a Marxist (ick!)

A couple of decades later Isaiah Berlin, who is a Russian refugee that fled the USSR in childhood (he saw the October Revolution) and who is a liberal and a strident anti-Marxist and anti-communist political theorist, delivers a speech titled “Two Concepts of Liberty”. You can guess what those two concepts happened to be. Berlin also happened to be fluent in German and he read a lot.

Is there direct evidence establishing the link between Erich Fromm’s writing and Isaiah Berlin’s speech? No.

But it’s not like Berlin one day wrote “Dear diary, today I am giving a speech and I thought I might as well plagiarise Erich Fromm…”