We do not, therefore, like Professor Bernheim, write exclusively for present and future specialists, but also for the public interested in history. We thus lay ourselves under an obligation to be as concise, as clear, and as little technical as possible. But to be concise and clear on subjects of this kind often means to appear superficial. Commonplace on the one hand, obscurity on the other: these, as we have already seen, are the evils between which we have the sorry privilege of choosing. We admit the difficulty. But we do not think it insurmountable, and our endeavour has been to say what we had to say in the clearest possible manner. The first half of the book has been written by M. Langlois, the second by M. Seignobos; but the two collaborators have constantly aided, consulted, and checked each other.[21] PARIS, _August 1897_. INTRODUCTION TO THE STUDY OF HISTORY BOOK I PRELIMINARY STUDIES CHAPTER I THE SEARCH FOR DOCUMENTS (HEURISTIC) The historian works with documents. Documents are the traces which have been left by the thoughts and actions of men of former times. Of these thoughts and actions, however, very few leave any visible traces, and these traces, when there are any, are seldom durable; an accident is enough to efface them. Now every thought and every action that has left no visible traces, or none but what have since disappeared, is lost for history; is as though it had never been. For want of documents the history of immense periods in the past of humanity is destined to remain for ever unknown. For there is no substitute for documents: no documents, no history.