In considering the historical value of any four documents, proof when they were written and who wrote them is, no doubt, highly important. For if proof exists, that A B C and D wrote them, and that they were intelligent persons, writing independently and without prejudice, about facts within their own knowledge--their statements must needs be worthy of the most attentive consideration.[4] But, even ecclesiastical tradition does not assert that either "Mark" or "Luke" wrote from his own knowledge--indeed "Luke" expressly asserts he did not. I cannot discover that any competent authority now maintains that the apostle Matthew wrote the Gospel which passes under his name. And whether the apostle John had, or had not, anything to do with the fourth Gospel; and if he had, what his share amounted to; are, as everybody who has attended to these matters knows, questions still hotly disputed, and with regard to which the extant evidence can hardly carry an impartial judge beyond the admission of a possibility this way or that. Thus, nothing but a balancing of very dubious probabilities is to be attained by approaching the question from this side. It is otherwise if we make the documents tell their own story: if we study them, as we study fossils, to discover internal evidence, of when they arose, and how they have come to be. That really fruitful line of inquiry has led to the statement and the discussion of what is known as the _Synoptic Problem_. In the Essays (VII.--XI.) which deal with the consequences of the application of the agnostic principle to Christian Evidences, contained in this volume, there are several references to the results of the attempts which have been made, during the last hundred years, to solve this problem. And, though it has been clearly stated and discussed, in works accessible to, and intelligible by, every English reader,[5] it may be well that I should here set forth a very brief exposition of the matters of fact out of which the problem has arisen; and of some consequences, which, as I conceive, must be admitted if the facts are accepted. These undisputed and, apparently, indisputable data may be thus stated: I. The three books of which an ancient, but very questionable, ecclesiastical tradition asserts Matthew, Mark, and Luke to be the authors, agree, not only in presenting the same general view, or _Synopsis_, of the nature and the order of the events narrated; but, to a remarkable extent, the very words which they employ coincide.