According to a wide-spread view science grows linearly and cumulatively. Brick is laid upon brick, and in this way the edifice of science is slowly but constantly growing. But studies of the history of science have shown that the development of science is far more dramatic. There are scientific revolutions which do not leave stone upon stone.¹ Thus the scientist is not only a master builder, but also a demolition expert; and science is growing like a modern town: old houses are destroyed and replaced by new ones.