Any such distribution of the kinds of proof is mere confusion, illogical abstractedly, and involving consequences, which, if acted upon, would appear ridiculously absurd.
It is indeed true that the three great classes of facts—the universal, or absolute (mathematical and metaphysical)—the general, or physical, and the individual (forensic and historical) are pursued and ascertained by three corresponding methods, or, as they might be called, three logics. But it is far from being true that the three species of reasoning hold an exclusive authority or sole jurisdiction over the three classes of facts above mentioned. Throughout the physical sciences the mathematical logic is perpetually resorted to, while even within the range of the mathematical the physical is, once and again, brought in as an aid. But if we turn to the historical and forensic department of facts, the three methods are so blended in the establishment of them, that to separate them altogether is impracticable; and as to moral evidence, if we use the phrase in any intelligible sense, it does but give its aid, at times, on this ground; and even then the conclusions to which it leads rest upon inductions which are physical, rather than moral.
The conduct of a complicated historical or forensic argument concerning individual facts, resembles the manipulations of an adroit workman, who, having some nice operation in progress, lays down one tool and snatches up another, and then another, according to the momentary exigencies of his task.
That sort of evidence may properly be called moral, which appeals to the moral sense, and in assenting to which, as we often do with an irresistible conviction, we are unable, with any precision, to convey to another mind the grounds of our firm belief. It is thus often that we estimate the veracity of a witness or judge of the reality or spuriousness of a written narrative. But then even this sort of evidence, when nicely analyzed, resolves itself into physical principles.
What are these convictions which we find it impossible to clothe in words, but the results in our minds, of slow, involuntary inductions concerning moral qualities, and which, inasmuch as they are peculiarly exact, are not to be transfused into a medium so vague and faulty as is language, at the best?
As to the mass of history, by far the larger portion of it rests, in no proper sense, upon moral evidence. To a portion the mathematical doctrine of probabilities applies—for it may be as a million to one—that an alleged fact, under all the circumstances, is true. But the proof of the larger portion resolves itself into our knowledge of the laws of the material world, and of those of the world of mind. A portion also is conclusively established by a minute scrutiny of its agreement with that intricate combination of small events which makes up the course of human affairs.
Every real transaction, especially those which flow on through a course of time, touches this web-work of small events at many points, and is woven into its very substance. Fiction may indeed paint its personages so as for a moment to deceive the eye, but it has never succeeded in the attempt to foist its factitious embroideries upon the tapestry of truth.
We might take as an instance that irresistible book in which Paley has established the truth of the personal history of St. Paul (“The Horæ Paulinæ”). It is throughout a tracing of the thousand fibres by which a long series of events connects itself with the warp and woof of human affairs. To apply to evidence of this sort, the besom of skepticism, and sweepingly to remove it as consisting only in moral evidence, is an amazing instance of confusion of mind.
It is often loosely affirmed that history rests mainly upon moral evidence. Is then a Roman camp moral evidence? Or is a Roman road moral evidence? Or are these and many other facts, when appealed to as proof of the assertion that, in a remote age, the Romans held military occupation of Britain, moral evidence? If they be, then we affirm that, when complete in its kind, it falls not a whit behind mathematical demonstration, as to its certainty.
Although it is not true that Christianity rests mainly upon moral evidence, yet it is true that it might rest on that ground with perfect security.