His dominating point was his passionate vocation; his worship of Science and of Reason made of him an inspired apostle. He had the faults and qualities of a rich and powerful nature. Vibrating through all the fibres of his being, he shed life and light around him. His temper was violent and passionate; he could bear no attack on the ideas which were dear to him, and became combative as soon as he thought them threatened. His was a wrestler's temperament; obstacles exasperated his energy and he went straight for them, pursuing his object with an invincible tenacity; he never gave up a problem, however difficult, and never hesitated to face any sacrifice or any privation if he thought them necessary. A strange contradiction with this iron will was offered by occasional disconcerting impulses, like that which caused the failure of his first journey abroad, or by sudden attacks of fury for insignificant reasons such as an unexpected noise in the street, a cat mewing or a dog barking, or angry impatience when he could not solve a frivolous puzzle, etc. This impulsive disposition gradually calmed down as he grew older, and ultimately very nearly disappeared. In his personal relations also he was apt to lose his temper, but a reaction very soon followed the outburst, and his efforts to be forgiven when he felt guilty were very touching. On the other hand, he did not easily forget an offence, though no desire for revenge ever soiled his soul, and his gratitude for kindness was absolutely indestructible. He harboured pessimistic theories to that extent that he looked upon the procreation of other lives as a crime on the part of a conscious being; his physical and moral sensitiveness was intense. And yet he had inherited from his mother a natural gaiety and delightful elasticity which always ended by gaining the upper hand. He was fond of joking; his wit was occasionally somewhat cutting, but that was entirely due to the appropriateness of his remarks; he never hurt people's feelings intentionally. He sometimes gave offence by a professional habit of using personal and concrete instances by way of arguments, but he applied the process to himself as well; it was the objective method, nothing more, and those who knew him well never doubted it.