For the first time the drama of the Château Jussat-Randon appeared real to his mind, for he was thinking of it with the most real part of his nature, his psychologic faculty. He forgot Dumoulin as well as the inconveniences of the possible journey to Riom, and his mind was completely absorbed by the moral problem which the crime presented. The first question would naturally have been: “Did Robert Greslon really assassinate Mlle. de Jussat?” But the philosopher did not think of that, yielding to this defect of generalizing minds, that never more than half verify the ideas upon which they speculate. Facts are, to them, only matter for theoretic using, and they distort them wilfully the better to build up their systems. The philosopher again took up the formula by which he summed up this drama: “A young man who becomes jealous and commits a murder, this is one more proof in support of my theory that the instinct of destruction and that of love awake at the same time in the male.” He had used this principle to write a chapter of extraordinary boldness on the aberrations of the generative faculty in his ‘Theory of the Passions.’ The reappearance of fierce animality among the civilized would alone suffice to explain this act. It would be necessary also to study the personal heredity of the assassin. He forced himself to see Robert Greslon without any other traits than those which confirmed the hypothesis already outlined in his mind. “Those very brilliant black eyes, those too vivacious gestures, that brusque manner of entering into relations with me, that enthusiasm in speaking to me, there was nervous derangement in this fellow. The father died young? If it could be proved that there was alcoholism in the family, then there would be a beautiful case of what Legrand Du Saulle calls _épilepsie larvée_. In this way his silence may be explained, and his denials may be sincere. This is the essential difference between an epileptic and the deranged. The last remembers his act, the epileptic forgets them. Would this then be a _larval epileptic_?” At this point of his reverie the philosopher experienced a moment of real joy. He had just constructed a building of ideas which he called an explanation, following the habit so dear to his race. He considered this hypothesis from different points, recalling several examples cited by his author in his beautiful treatise on forensic medicine, until he arrived at the Jardin des Plantes, which he entered by the large gate of the Quay Saint Bernard.