When it ran into something that its knowledge couldn't account for, it asked questions. Lenat answered them. Cyc's mind is like an exhaustively cross-referenced encyclopedia. Every thrush is a bird. Every hummingbird is a bird.
Every raven is a bird.
Every ibis is a bird. Further on, the rules become increasingly precise. X evokes positive sympathy. In other words, if a person sees a bird that is suffering, that person will usually feel sorry for the bird. Some have a weirdly insightful quality.