Grammar of Assent

This certitude and this evidence are often called moral; a word which I avoid, as having a very vague meaning; but using it here for once, I observe that moral evidence and moral certitude are all that we can attain, not only in the case of ethical and spiritual subjects, such as religion, but of terrestrial and cosmical questions also. So far, physical Astronomy and Revelation stand on the same footing. Vince, in his treatise on Astronomy, does but use the language of philosophical sobriety, when, after speaking of the proofs of the earth's rotatory motion, he says, "when these reasons, all upon different principles, are considered, they amount to a proof of the earth's rotation about its axis, which is as satisfactory to the mind as the most direct demonstration could be;" or, as he had said just before, "the mind rests equally satisfied, as if the matter was strictly proved." [Note 9] That is, first there is no demonstration that the earth rotates; next there is a cluster of "reasons on different principles," that is, independent probabilities in cumulation: thirdly, these "amount to a proof," and "the mind" feels "as if the matter was strictly proved," that is, there is the equivalent of proof; lastly, "the mind rests satisfied," that is, it is certain on the point. And though evidence of the fact is now obtained which was not known fifty years ago, that evidence on the whole has not changed its character.

Compare with this avowal the language of Butler, when discussing the proof of Revelation. "Probable proofs," he says, "by being added, not only increase the evidence, but multiply it. The truth of our religion, like the truth of common matters, is to be judged by the whole evidence taken together... in like manner as, if in any common case numerous events acknowledged were to be alleged in proof of any other event disputed, the truth of the disputed event would be proved, not only if any one of the acknowledged ones did of itself clearly imply it, but though no one of them singly did so, if the whole of the acknowledged events taken together could not in reason be supposed to have happened, unless the disputed one were true." [Note 10] Here, as in Astronomy, is the same absence of demonstration of the thesis, the same cumulating and converging indications of it, the same indirectness in the proof, as being per impossibile, the same recognition nevertheless that the conclusion is not only probable, but true. One other characteristic of the argumentative process is given, which is unnecessary in a subject-matter so clear and simple as astronomical science, viz. the moral state of the parties inquiring or disputing. They must be "as much in earnest about religion, as about their temporal affairs, capable of being convinced, on real evidence, that there is a God who governs the world, and feel themselves to be of a moral nature and accountable creatures." [Note 11]

This being the state of the case, the question arises, whether, granting that the personality (so to speak) of the parties reasoning is an important element in proving propositions in concrete matter, any account can be given of the ratiocinative method in such proofs, over and above that analysis into syllogism which is possible in each of its steps in detail. I think there can; though I fear, lest to some minds it may appear far-fetched or fanciful; however, I will hazard this imputation. I consider, then, that the principle of concrete reasoning is parallel to the method of proof which is the foundation of modern mathematical science, as contained in the celebrated lemma with which Newton opens his "Principia." We know that a regular polygon, inscribed in a circle, its sides being continually diminished, tends to become that circle, as its limit; but it vanishes before it has coincided with the circle, so that its tendency to be the circle, though ever nearer fulfilment, never in fact gets beyond a tendency. In like manner, the conclusion in a real or concrete question is foreseen and predicted rather than actually attained; foreseen in the number and direction of accumulated premisses, which all converge to it, and as the result of their combination, approach it more nearly than any assignable difference, yet do not touch it logically (though only not touching it,) on account of the nature of its subject-matter, and the delicate and implicit character of at least part of the reasonings on which it depends. It is by the strength, variety, or multiplicity of premisses, which are only probable, not by invincible syllogisms,—by objections overcome, by adverse theories neutralized, by difficulties gradually clearing up, by exceptions proving the rule, by un-looked-for correlations found with received truths, by suspense and delay in the process issuing in triumphant reactions,—by all these ways, and many others, it is that the practised and experienced mind is able to make a sure divination that a conclusion is inevitable, of which his lines of reasoning do not actually put him in possession. This is what is meant by a proposition being "as good as proved," a conclusion as undeniable "as if it were proved," and by the reasons for it "amounting to a proof," for a proof is the limit of converging probabilities.

It may be added, that, whereas the logical form of this argument, is, as I have already observed, indirect, viz. that "the conclusion cannot be otherwise," and Butler says that an event is proved, if its antecedents "could not in reason be supposed to have happened unless it were true," and law-books tell us that the principle of circumstantial evidence is the reductio ad absurdum, so Newton too is forced to the same mode of proof for the establishment of his lemma, about prime and ultimate ratios. "If you deny that they become ultimately equal," he says, "let them be ultimately unequal;" and the consequence follows, "which is against the supposition."

Such being the character of the mental process in concrete reasoning, I should wish to adduce some good instances of it in illustration, instances in which the person reasoning confesses that he is reasoning on this very process, as I have been stating it; but these are difficult to find, from the very circumstance that the process from first to last is carried on as much without words as with them. However, I will set down three such.

1. First, an instance in physics. Wood, treating of the laws of motion, thus describes the line of reasoning by which the mind is certified of them. "They are not indeed self-evident, nor do they admit of accurate proof by experiment, on account of the effects of friction and the air's resistance, which cannot entirely be removed. They are, however, constantly and invariably suggested to our senses, and they agree with experiment, as far as experiment can go; and the more accurately the experiments are made, and the greater care we take to remove all those impediments which tend to render the conclusions erroneous, the more nearly do the experiments coincide with these laws.

"Their truth is also established upon a different ground: from these general principles innumerable particular conclusions have been deducted; sometimes the deductions are simple and immediate, sometimes they are made by tedious and intricate operations; yet they are all, without exception, consistent with each other and with experiment. It follows thereby, that the principles upon which the calculations are founded are true." [Note 12]

The reasoning of this passage (in which the uniformity of the laws of nature is assumed) seems to me a good illustration of what must be considered the principle or form of an induction. The conclusion, which is its scope, is, by its own confession, not proved; but it ought to be proved, or is as good as proved, and a man would be irrational who did not take it to be virtually proved; first, because the imperfections in the proof arise out of its subject-matter and the nature of the case, so that it is proved interpretativè; and next, because in the same degree in which these faults in the subject-matter are overcome here or there, are the involved imperfections here or there of the proof remedied; and further, because, when the conclusion is assumed as an hypothesis, it throws light upon a multitude of collateral facts, accounting for them, and uniting them together in one whole. Consistency is not always the guarantee of truth; but there may be a consistency in a theory so variously tried and exemplified as to lead to belief in it, as reasonably as a witness in a court of law may, after a severe cross-examination, satisfy and assure judge, jury, and the whole court, of his simple veracity.

2. And from the courts of law shall my second illustration be taken.

9. Pp. 84, 85.

10. "Analogy," pp. 329, 330, ed. 1836.

11. Ibid. p. 278.

12. "Mechanics," p. 31.