 Suppose that a defendant were allowed to testify that, before acting, he considered carefully what would be the conduct of a prudent man under the circumstances, and, having formed the best judgment he could, acted accordingly. If the story was believed, it would be conclusive against the defendant’s negligence judged by a moral standard which would take his personal characteristics into account. But supposing any such evidence to have got before the jury, it is very clear that the court would say, Gentlemen, the question is not whether the defendant thought his conduct was that of a prudent man, but whether you think it was. (1881: 107) 