If categorization is central to thinking, then what mechanism carries it out? Analogy is the answer. - Douglas Hofstadter

Some of us, perhaps all of us, believe that it is legitimate to kill enemy soldiers in a war, as if war were a special circumstance that shrinks the sizes of enemy souls.

Concepts in the brains of humans acquired the property that they could get rolled together with other concepts into larger packets, and any such larger packet could then become a new concept in its own right. In other words, concepts could nest inside each other hierarchically, and such nesting could go on to arbitrary degrees.

And one of my firmest conclusions is that we always think by seeking and drawing parallels to things we know from our past, and that we therefore communicate best when we exploit examples, analogies, and metaphors galore, when we avoid abstract generalities, when we use very down-to-earth, concrete, and simple language, and when we talk directly about our own experience.