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    Even animals need predictive powers.  To see into the future,

    simple creatures like the frog have a pre-wired model of the world.

    The frog is built with a set of neural trip-lines between his eye, the

    visual processors in his brain, and his tongue.   These nerve cells are

    constructed to follow a set of simple instructions: erratically moving

    object? Flick tongue.  Motionless object: don't bother.  It works.  The

    frog ends up with food.  His nerves embody a model of a planet in

    which objects flitting by are usually delicious.

    But the frog's pre-wired picture of the world will not change with

    circumstances.  Offer a starving frog an immobilized fly and he simply

    will not touch it.  His built-in portrait of the universe tells him that only

    objects which dart around are fit for dinner.  If a captive frog goes on

    long enough ignoring the torpid bits of nourishment offered him, the

    flaws in his unbending world-model could kill him.68

    More complex animals, on the other hand, build parts of their

    models on experience.  Their pictures of the invisible world are

    changeable.  A dog is capable of quickly developing a model of things

    it's never seen before. Lock the hound in a room it's never visited, and

    the beast will immediately check out all the details, building up an

    image of the place, searching for an exit it's never even glimpsed.

    Thanks to an ability to imagine walls and doorways it has never seen,

    the curious canine is able to predict the existence of an escape route.69

    Albert Einstein used the mathematical model provided by

    Bernhard Riemann to predict everything from the energy in the atom

    to the motion of light.  But instead of employing math to construct

    models, our minds most often use metaphors.70  Our brains are

    picture-making machines.  Every culture has a worldview, not an

    algebraic set of cosmic calculations.  Uneducated medieval Christians

    pictured the earth as a flat disk which ended somewhere over the

    watery horizon.  They predicted that small boats which sailed too far

    from the Atlantic shore would never be seen again.  Renaissance

    intellectuals, on the other hand, revived the old Greek image of the

    terrestrial surface as a sphere.  To Columbus, this meant that he might

    sail off into the western sunset and emerge with the sunrise on the

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