> intellectual societies decay as they begin to rely on secondary-source research (going to the library and reading what people have written about others' exper

> intellectual societies decay as they begin to rely on secondary-source research (going to the library and reading what people have written about others' experiences, instead of going out there yourself and looking at stuff I have to assume that Asimov was thinking about the course of history from the classical period through to the Enlightenment here, as it is conventionally told. Back in the day, the Greeks etc actually looked at things, and thought about them, and wrote down what they came up with. Some of it was good (mathematics), some bad (biology). But then at some point that stopped, and people relied entirely on the books the Greeks had written. Aristotle was the ultimate authority on natural science for centuries. Until the Enlightenment came along, and people started doing experiments and observations and exploration again. I'm sure modern historians will fall over themselves to tell you this isn't true (it leaves out the Arabs, for a start, but it probably isn't even entirely true of Europe), but that's the story of history that Asimov would have known.