_Extent of the Science._--The field covered by the study of diplomatic is so extensive and the different kinds of documents which it takes into its purview are so numerous and various, that it is impossible to do more than give a few general indications of their nature. No nation can have advanced far on the path of civilization before discovering the necessity for documentary evidence both in public and in private life. The laws, the constitutions, the decrees of government, on the one hand, and private contracts between man and man, on the other, must be embodied in formal documents, in order to ensure permanent record. In the case of a nation advancing independently from a primitive to a later stage of civilization we should have to trace the origin of its documentary records and examine their development from a rudimentary condition. But in an inquiry into the history of the documents of the middle ages in Europe we do not begin with primitive forms. Those ages inherited the documentary system which had been created and developed by the Romans; and, imperfect and limited in number as are the earliest surviving charters and diplomas of European medieval history, they present themselves to us fully developed and cast in the mould and employing the methods and formulae of the earlier tradition. Based on this foundation the chanceries of the several countries of Europe, as they came into existence and were organized, reduced to method and rule on one general system the various documents which the exigencies of public and of private life from time to time called into existence, each individual chancery at the same time following its own line of practice in detail, and evolving and confirming particular formulas which have become characteristic of it.
_Classification of Documents._--If we classify these documents under the two main heads of public and private deeds, we shall have to place in the former category the legislative, administrative, judicial, diplomatic documents emanating from public authority in public form: laws, constitutions, ordinances, privileges, grants and concessions, proclamations, decrees, judicial records, pleas, treaties; in a word, every kind of deed necessary for the orderly government of a civilized state. In early times many of these were comprised under the general term of "letters," _litterae_, and to the large number of them which were issued in open form and addressed to the community the specific title of "letters patent," _litterae patentes_, was given. In contradistinction those public documents which were issued in closed form under seal were known as "close letters," _litterae clausae_.