COLIN MCHINN proposes a taxonomy of ideas that invokes a three-way division: memes, dreams and themes. It is characteristic of ideas to be shared by many minds. A meme spreads like a virus from one mind to another, duplicating itself, colonizing new minds. We are immersed in memes — jingles, catchphrases, fads, fashions, crazes, religions, ideologies, mannerisms and accents. They spread by imitation and natural credulity, exploiting the receptivity of the human mind to new information and influence, forged in childhood. Uncritical copying is favored. People just can’t help picking stuff up. One of the central questions of civilized life is which of one’s existing ideas are memes and which are themes: Which are absorbed because of mental manipulation and which represent genuine value — scientific, moral, or aesthetic?