Professor Royce can offer to make it credible that a man on hearing of the death of a friend should straightway be capable of imagining that at a definite hour and in a particular place he had seen an apparition of that friend, when in fact he had had no experience of the kind. It is remarkable that Mr. Royce does not himself appear to have realised the distinction between the two kinds of impressions. _Precautions against Error._ We have now to consider by what methods the various defects incident to testimony on these matters may be best eliminated. As the evidence upon which reliance is placed will be illustrated by the examples quoted hereafter, it will not be necessary to dwell at length here upon the precautions taken. The testimony at first-hand of the actual witnesses, it need hardly be said, is to be desired in any investigation; but in the case of phenomena which are at once stimulating to the imagination, and, as being novel, have no recognised standard of probability by which narrator or auditor can check deviations from the truth, no other evidence is worthy of consideration.[79] It will be seen that in all the cases here quoted the witness, or one of the witnesses, has furnished an account of his experience written by himself;[80] and it is worth noting that the very act of writing such an account to serve the purpose of a systematic inquiry is calculated to inspire the percipient with a sense of responsibility, and to lead him to weigh his words with precision. I may add that by the courtesy of our informants we have in most cases been enabled to question them orally on the details of their experience.[81]