A peasant who is weather-wise may be simply unable to assign intelligible reasons why he thinks it will be fine to-morrow; and if he attempts to do so, he may give reasons wide of the mark; but that will not weaken his own confidence in his prediction. His mind does not proceed step by step, but he feels all at once the force of various combined phenomena, though he is not conscious of them. Again, there are physicians who excel in the _diagnosis_ of complaints; though it does not follow from this, that they could defend their decision in a particular case against a brother physician who disputed it. They are guided by natural acuteness and varied experience; they have their own idiosyncratic modes of observing, generalizing, and concluding; when questioned, they can but rest on their own authority, or appeal to the future event. In a popular novel,(25) a lawyer is introduced, who “would know, almost by instinct, whether an accused person was or was not guilty; and he had already perceived by instinct” that the heroine was guilty. “I’ve no doubt she’s a clever woman,” he said, and at once named an attorney practising at the Old Bailey. So, again, experts and detectives, when employed to investigate mysteries, in cases whether of the civil or criminal law, discern and follow out indications which promise solution with a sagacity incomprehensible to ordinary men. A parallel gift is the intuitive perception of character possessed by certain men, while others are as destitute of it, as others again are of an ear for music. What common measure is there between the judgments of those who have this intuition, and those who have not? What but the event can settle any difference of opinion which occurs in their estimation of a third person? These are instances of a natural capacity, or of nature improved by practice and habit, enabling the mind to pass promptly from one set of facts to another, not only, I say, without conscious media, but without conscious antecedents. Sometimes, I say, this illative faculty is nothing short of genius. Such seems to have been Newton’s perception of truths mathematical and physical, though proof was absent. At least that is the impression left on my own mind by various stories which are told of him, one of which was stated in the public papers a few years ago. “Professor Sylvester,” it was said, “has just discovered the proof of Sir Isaac Newton’s rule for ascertaining the imaginary roots of equations.... This rule has been a Gordian-knot among algebraists for the last century and a half. The proof being wanting, authors became ashamed at length of advancing a proposition, the evidence for which rested on no other foundation than belief in Newton’s sagacity.(26)”