We can reconstruct, to some extent, these phases of prehistoric life. Our greatest difficulties begin when we attempt to combine these separate parts in one pattern or picture, to trace their chronological succession or the extent of their overlappings and their mutual influence and relations in custom and thought. Here, we admit, our knowledge is still very vague and inadequate. Twenty years ago the problem seemed insoluble; perhaps it still remains so. But during that time explorations, investigations, and study have given us many most important facts and suggestions. Some inferences we can accept with a fair degree of confidence, others have varying degrees of probability, sometimes we can only guess. But guesses do no harm, if acknowledged and recognized as such. I venture to hope that historian and sociologist may find valuable facts and suggestions in this book. But, while writing it, I have thought more often of the eager young student who may glance over its pages, feel the allurement of some topic and resolve to know more about it. The bibliography is prepared especially for him. It is anything but complete. The literature of the period is almost endless. I have referred to only a few of the best and most suggestive works. They will introduce him to a chain of others. If he studies their facts and arguments he will probably reject some of my opinions or theories, modify others, and form his own. If I can do any young student this service, my work will have been amply repaid. America has sent few laborers into this rich harvest field. I wish that this little book might play the part of a good host, and introduce many intelligent, thoughtful, and puzzled readers to the company and view-point of the prehistorian. In prehistory we find man entering upon course after course of hard and rigid discipline and training, usually under the spur of necessity, the best of all teachers. Every course lasts through millennia. Their chief end is to socialize and humanize individual men. Environment, natural or artificial, is a means to this end. It compels men to struggle, each with himself; only as men improve is any marked change of conditions possible or desirable. Men must "pass" in the lower course before they can be promoted to the next higher, to find here a similar field of struggle on a somewhat higher plane. Human evolution, as a process of humanizing and socializing man, is and must be chiefly ethical; for ethics is nothing more nor less than the science and art of living rightly with one's neighbor. And man is incurably religious, always feeling after the power or powers in or behind nature, whose essential character she is compelling him to express, as her inadequate but only mouthpiece. He will gradually become like what he is feeling after, dimly recognizing, and rudely worshipping. These are the most important departments of the school of prehistoric man.