So, yes, he explicitly mentioned something, that's why I mentioned too.
What I think the problem is that he implies in that sentence that either reading is more instructionless than hearing/talking, or that somehow good instruction itself should just grow on trees, or that instruction is always good, or that ratio of instructioned knowledge vs "ignorance" matters.
What I try to point out is that what matters is applied knowledge, which is still very rare even today, yet the chance of picking up a book that helps with acquiring the skills to gather and apply knowledge has more chance than hearing it from someone.