(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 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, 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.