And here, I think, it will not be unadvisable to pause for a moment, and endeavour to ascertain what misconceived truth lay at the root of this fatal tenet. Considered abstractedly and by the light of nature, it is as unmeaning to speak of the immorality of an intellectual mistake as it would be to talk of the colour of a sound. If a man has sincerely persuaded himself that it is possible for parallel lines to meet, or for two straight lines to enclose a space, we pronounce his judgment to be absurd; but it is free from all tincture of immorality. And if, instead of failing to appreciate a demonstrable truth, his error consisted in a false estimate of the conflicting arguments of an historical problem, this mistake—assuming always that the enquiry was an upright one—is still simply external to the sphere of morals. It is possible that his conclusion, by weakening some barrier against vice, may produce vicious consequences, like those which might ensue from some ill-advised modification of the police force; but it in no degree follows from this that the judgment is in itself criminal. If a student applies himself with the same dispositions to Roman and Jewish histories, the mistakes he may make in the latter are no more immoral than those which he may make in the former. There are, however, two cases in which an intellectual error may be justly said to involve, or at least to represent, guilt. In the first place, error very frequently springs from the partial or complete absence of that mental disposition which is implied in a real love of truth. Hypocrites, or men who through interested motives profess opinions which they do not really believe, are probably rarer than is usually supposed; but it would be difficult to over-estimate the number of those whose genuine convictions are due to the unresisted bias of their interests. By the term interests, I mean not only material well-being, but also all those mental luxuries, all those grooves or channels for thought, which it is easy and pleasing to follow, and painful and difficult to abandon. Such are the love of ease, the love of certainty, the love of system, the bias of the passions, the associations of the imagination, as well as the coarser influences of social position, domestic happiness, professional interest, party feeling, or ambition. In most men, the love of truth is so languid, and the reluctance to encounter mental suffering is so great, that they yield their judgments without an effort to the current, withdraw their minds from all opinions or arguments opposed to their own, and thus speedily convince themselves of the truth of what they wish to believe. He who really loves truth is bound at least to endeavour to resist these distorting influences, and in as far as his opinions are the result of his not having done so, in so far they represent a moral failing.