If it takes 200 years to achieve artificial intelligence, and then finally there is a textbook that explains how it's done, the hardest part of that textbook to write will be the part that explains why people didn't think of it 200 years ago. Because we're really talking about how to make machines do things that are really on the surface of our minds.

It's just that our ability to observe our own mental processes is not very good and has not been very good. When we look at Leibniz, he invented binary numbers, but he didn't even invent propositional calculus that was invented by Boole 150 years later. And then Boole didn't invent predicate calculus.

So what one sees is that each step in understanding of thought processes has taken time.