Major challenges, however, are too serious to be met with argument, or with sharpened explanation. They call either for outright and wholesale rejection, or for conversion. One does not cross over from Manichaeism to Christianity, or from Lamarckianism to Darwinism, by a mere adjustment of views. True conversions consist in the choice of a new audience, that is, of a new world. All that was once familiar is now seen in startlingly new ways.
