I don't know, maybe the good old separation between soft and hard science can help here. On the speech side, in soft science, I think the most powerful transmis

I don't know, maybe the good old separation between soft and hard science can help here. On the speech side, in soft science, I think the most powerful transmission of knowledge if by pure speech, oral speech, like in podcasts. A good lecturer will branch his brain on yours and will have a very high and precise throughput, only by spoken words. That's for history, politics, philosophy, soft sciences. The best example I know of this effect is the courses of Jankelevitch (in French), it's really like a good ride on the back of an experimented motorbike driver knowing the region like the back of his hand. On the other side, the pinnacle of hard sciences, geometry, logic, topology, are very visual and symbolic by essence. A proof is only an explanation of a truth that is already there, that some can "see in their mind". I wouldn't imagine being able to follow a math class without a black board, that would be like a piano lesson without a piano.