The struggle among ideas produces both triumph and tragedy. People rarely ask the important questions about their culture: What are the controlling ideas, where did they come from, how have they evolved, and why are they believed? There may not be ultimate, finite answers to some of these questions and, in fact, no matter how certain one may be about any conceptual system, it can soon be reduced to paradox if questioned too closely.. Without a clear understanding of the origin and evolution of concepts over the course of history, it is difficult to appreciate why earlier individuals and societies behaved in ways that may seem bizarre to modern individuals.. Human history has been a continual test of conceptual models, including everything from cannibalism to communism, and those that prevailed in any era provided the justification for behavior of the community. The growth and decline of religions, nations, economies, and civilizations can ultimately be traced to competitions among ideas....