Man has ever been the greatest puzzle to man. There are many and important reasons for this fact. As the subject of this book is not a theoretical, academic study of man, of which too many have already been written, I will not recount the reasons, but will confine myself to the more pressing matters of the task in hand, which is that of pointing the way to the science and art of Human Engineering. The two facts which have to be dealt with first, are the two which have most retarded human progress: (1) there has never been a true definition of man nor a just conception of his rôle in the curious drama of the world; in consequence of which there has never been a proper principle or starting point for a science of humanity. It has never been realized that man is a being of a dimension or type different from that of animals and the characteristic nature of man has not been understood; (2) man has always been regarded either as an animal or as a supernatural phenomenon. The facts are that man is not _super_natural but is literally a part of nature and that human beings are not animals. We have seen that the animals are truly characterized by their autonomous mobility—their space-binding capacity—animals are space-binders. We have seen that human beings are characterized by their creative power, by the power to make the past live in the present and the present for the future, by their capacity to bind time—human beings are time-binders. These concepts are basic and impersonal; arrived at mathematically, they are mathematically correct. It does not matter at all _how_ the first man, the first time-binder, was produced; the fact remains that he was somewhere, somehow produced. To know anything that is to-day of fundamental interest about man, we have to analyse man in three coordinates—in three capacities; namely, his chemistry, his activities in space, and especially his activities in time; whereas in the study of animals we have to consider only two factors: their chemistry and their activities in space.