I wish to introduce my discussion of this question by quoting a passage in which Professor James seems to me to say something which is indisputably true. Towards the end of Lecture VI, he attacks the view that truths "have an unconditional claim to be recognised." And in the course of his attack the following passage occurs:-- "Must I," he says, "constantly be repeating the truth 'twice two are four' because of its eternal claim on recognition? or is it sometimes irrelevant? Must my thoughts dwell night and day on my personal sins and blemishes, because I truly have them?--or may I sink and ignore them in order to be a decent social unit, and not a mass of morbid melancholy and apology?" "It is quite evident," he goes on, "that our obligation to acknowledge truth, so far from being unconditional, is tremendously conditional. Truth with a big T, and in the singular, claims abstractly to be recognised, of course; but concrete truths in the plural need be recognised only when their recognition is expedient." (pp. 231-232). What Professor James says in this passage seems to me so indisputably true as fully to justify the vigour of his language. It is as clear as anything can be that it would not be useful for any man's mind to be _always_ occupied with the true idea that he had certain faults and blemishes; or to be _always_ occupied with the idea that twice two are four. It is clear, that is, that, if there are times at which a particular true idea is useful, there certainly are other times at which it would _not_ be useful, but positively in the way. This is plainly true of nearly all, if not quite all, our true ideas. It is plainly true with regard to nearly all of them that, even if the occasions on which their occurrence is useful are many, the occasions on which their occurrence would _not_ be useful are many more. With regard to most of them it is true that on most occasions they will, as Professor James says elsewhere, "be practically irrelevant, and had better remain latent." It is, then, quite clear that almost any particular true idea _would_ not be useful at all times and that the times at which it would _not_ be useful, are many more than the times at which it would. And what we have to consider is whether, in just this sense in which it is so clear that most true ideas would _not_ be useful at most times, it is nevertheless true that all our true ideas _are_ useful. Is this so? Are all our true ideas useful?