The fundamental flaw with Lenat's approach is that humans do not think with first order predicate calculus. We do not juggle a bunch of statements/rules the way Cyc does, but have a very fast, efficient and powerful conceptual approach to the world with a massive amount of recursive conceptual inference.

Effectively, you need to understand (compute with) what concepts are before using them in statements. And the most common mistake is to confuse the definition of a concept with the concept itself, as happens typically with knowledge graphs.