The rules of deductive logic are inculcated throughout our intellectual education. They are universally accepted. They provide firm standards of judgement for many aspects of academic study, research, and of our daily work. It is from some points of view perhaps a matter of regret—and from others of challenge–that their scope is not all-embracing, and that a wide range of problems, both of practical affairs and of intellectual inquiry, is beyond their jurisdiction. These problems, of which the subject-matter of this essay is one, involve the process known as induction, or inductive logic. Rules, standards of judgement, do exist in this field, but few have won universal acceptance and many are the subject of vigorous philosophical dispute.