Of course present knowledge of psychology is nearer to zero than to complete perfection, and its applications to teaching must therefore be often incomplete, indefinite, and insecure. The application of psychology to teaching is more like that of botany and chemistry to farming than like that of physiology and pathology to medicine. Anyone of good sense can farm fairly well without science, and anyone of good sense can teach fairly well without knowing and applying psychology. Still, as the farmer with the knowledge of the applications of botany and chemistry to farming is, other things being equal, more successful than the farmer without it, so the teacher will, other things being equal, be the more successful who can apply psychology, the science of human nature, to the problems of the school. (pp. 9-10)