This chapter is a more analytical and penetrating treatment of the reasons why any study of human affairs must rely heavily on a comparative attitude of mind and on comparative techniques. To that extent it is more theoretical. Readers who find it heavy going, or who are already persuaded of the utility of comparative studies, can either dash through it or leave it alone, perhaps returning later. But as a justification for the approach used in this book and as a corrective of some fallacies of theory which can have dangerous consequences when they are applied to practical matters of political or educational decision, the advice given here claims the attention of any student of methodology in the social sciences, and above all of anyone engaged in comparative studies of education. It is not suggested that the ideas presented are new in their essence, though they may be new in their application to comparative education. But even the most seasoned student of methodology in the social sciences generally may do well to consider how tricky the applications of his methods become when the field of research is involved with so many problems of perception, and when the area of decision is so much entangled with the irrational, as the educational arena is to-day.