(4.) Again; very numerous are the cases, in which good arguments, and really good as far as they go, and confessed by us to be good, nevertheless are not strong enough to incline our minds ever so little to the conclusion at which they point. But why is it that we do not assent a little, in proportion to those arguments? On the contrary, we throw the full onus probandi on the side of the conclusion, and we refuse to assent to it at all, until we can assent to it altogether. The proof is capable of growth; but the assent either exists or does not exist.
(5.) I have already alluded to the influence of moral motives in hindering assent to conclusions which are logically unimpeachable. According to the couplet,—
“A man convinced against his will
Is of the same opinion still;”—
assent then is not the same as inference.
(6.) Strange as it may seem, this contrast between inference and assent is exemplified even in the province of mathematics. Argument is not always able to command our assent, even though it be demonstrative. Sometimes of course it forces its way, that is, when the steps of the reasoning are few, and admit of being viewed by the mind altogether. Certainly, one cannot conceive a man having before him the series of conditions and truths on which it depends that the three [pg 170] angles of a triangle are together equal to two right angles, and yet not assenting to that proposition. Were all propositions as plain, though assent would not in consequence be the same act as inference, yet it would certainly follow immediately upon it. I allow then as much as this, that, when an argument is in itself and by itself conclusive of a truth, it has by a law of our nature the same command over our assent, or rather the truth which it has reached has the same command, as our senses have. Certainly our intellectual nature is under laws, and the correlative of ascertained truth is unreserved assent.
But I am not speaking of short and lucid demonstrations; but of long and intricate mathematical investigations; and in that case, though every step may be indisputable, it still requires a specially sustained attention and an effort of memory to have in the mind all at once all the steps of the proof, with their bearings on each other, and the antecedents which they severally involve; and these conditions of the inference may interfere with the promptness of our assent.
Hence it is that party spirit or national feeling or religious prepossessions have before now had power to retard the reception of truths of a mathematical character; which never could have been, if demonstrations were ipso facto assents. Nor indeed would any mathematician, even in questions of pure science, assent to his own conclusions, on new and difficult ground, and in the case of abstruse calculations, however often he went over his work, till he had the corroboration of other judgments besides his own. He would have carefully revised his inference, [pg 171] and would assent to the probability of his accuracy in inferring, but still he would abstain from an immediate assent to the truth of his conclusion. Yet the corroboration of others cannot add to his perception of the proof; he would still perceive the proof, even though he failed in gaining their corroboration. And yet again he might arbitrarily make it his rule, never to assent to his conclusions without such corroboration, or at least before the lapse of a sufficient interval. Here again inference is distinct from assent.
I have been showing that inference and assent are distinct acts of the mind, and that they may be made apart from each other. Of course I cannot be taken to mean that there is no legitimate or actual connexion between them, as if arguments adverse to a conclusion did not naturally hinder assent; or as if the inclination to give assent were not greater or less according as the particular act of inference expressed a stronger or weaker probability; or as if assent did not always imply grounds in reason, implicit, if not explicit, or could be rightly given without sufficient grounds. So much is it commonly felt that assent must be preceded by inferential acts, that obstinate men give their own will as their very reason for assenting, if they can think of nothing better; “stat pro ratione voluntas.” Indeed, I doubt whether assent is ever given without some preliminary, which stands for a reason; but it does not follow from this, that it may not be withheld in cases when there are good reasons for giving it to a proposition, or may not be withdrawn after it has been given, the reasons remaining, or may not remain when the reasons are forgotten; [pg 172] or must always vary in strength, as the reasons vary; and this substantiveness, as I may call it, of the act of assent is the very point which I have wished to establish.
2. And in showing that assent is distinct from an act of inference, I have gone a good way towards showing in what it differs from it. If assent and inference are each of them the acceptance of a proposition, but the special characteristic of inference is that it is conditional, it is natural to suppose that assent is unconditional. Again, if assent is the acceptance of truth, and truth is the proper object of the intellect, and no one can hold conditionally what by the same act he holds to be true, here too is a reason for saying that assent is an adhesion without reserve or doubt to the proposition to which it is given. And again, it is to be presumed that the word has not two meanings: what it has at one time, it has at another. Inference is always inference; even if demonstrative, it is still conditional; it establishes an incontrovertible conclusion on the condition of incontrovertible premisses. To the conclusion thus drawn, assent gives its absolute recognition. In the case of all demonstrations, assent, when given, is unconditionally given. In one class of subjects, then, assent certainly is always unconditional; but if the word stands for an undoubting and unhesitating act of the mind once, why does it not denote the same always? what evidence is there that it ever means any thing else than that which the whole world will unite in witnessing that it means in certain cases? why are we not to interpret what is controverted by what is known? This is what is suggested [pg 173] on the first view of the question; but to continue:—