Our discussions were interminable, and we were always resuming the same subject. We passed part of the night in searching out together the topics upon which we were engaged. After some little time, M. Berthelot, having completed his special mathematical studies at the Lycée Henri IV., went back to his father, who lived at the foot of the Tour Saint Jacques de la Boucherie. When he came to see me in the evening at the Rue de l'Abbé de l'Épée, we used to converse for hours, and then I used to walk back with him to the Tour Saint Jacques. But as our conversation was rarely concluded when we got back to his door, he returned with me, and then I went back with him, this game of battledore and shuttlecock being renewed several times. Social and philosophical questions must be very hard to solve, seeing that we could not with all our energy settle them. The crisis of 1848 had a very great effect upon us. This fateful year was not more successful than we had been in solving the problems which it had set itself, but it demonstrated the fragility of many things which were supposed to be solid, and to young and active minds it seemed like the lowering of a curtain of clouds upon the horizon.
The profound affection which thus bound M. Berthelot and myself together was unquestionably of a very rare and singular kind. It so happened that we were both of an essentially objective nature; a nature, that is to say, perfectly free from the narrow whirlwind which converts most consciences into an egotistical gulf like the conical cavity of the formica-leo. Accustomed each to pay very little attention to himself, we paid very little attention to one another. Our friendship consisted in what we mutually learnt, in a sort of common fermentation which a remarkable conformity of intellectual organization produced in us in regard to the same objects. Anything which we had both seen in the same light seemed to us a certainty. When we first became acquainted, I still retained a tender attachment for Christianity. Berthelot also inherited from his father a remnant of Christian belief. A few months sufficed to relegate these vestiges of faith to that part of our souls reserved for memory. The statement that everything in the world is of the same colour, that there is no special supernatural or momentary revelation, impressed itself upon our minds as unanswerable. The scientific purview of a universe in which there is no appreciable trace of any free will superior to that of man became, from the first months of 1846, the immovable anchor from which we never shifted. We shall never move from this position until we shall have encountered in nature some one specially intentional fact having its cause outside the free will of man or the spontaneous action of the animal.