There are no monogamous animals save those which love only once during their lifetime. Exceptions to this rule have not sufficient constancy to be erected into a counter-rule. There are monogamists in fact, there are none of necessity, from the time an animal lives long enough to commit the reproductive act several times. Free female mammals nearly always flee the male who has once served them, they need a new one. A bitch does not receive last season's dog save in direst extremity. This appears to me to be the struggle of the specie against variety. The couple is the maker of varieties. Polygamy drags them back to the general type of the specie. Individuals of a specie frankly polygamous should present a very great similarity; if the species incline toward a certain monogamy, the dissemblances become more numerous. It is not an illusion which makes us recognize in human races almost monogamous, a lesser uniformity of type than in polygamous societies or those given over to promiscuity, or among animal species. The example of the dog seems the worst that one could have chosen. It isn't, it is the best, considering that in receiving successively individuals of different variety, the bitch tends to produce individuals not of a specialized breed, but on the contrary of a type where several breeds will be mixed, individuals which in crossing and recrossing in their turn, will end, if the dogs live in a free state, in forming one single specie. Sexual liberty tends to establish uniformity of type; monogamy strives against this tendency and maintains diversity.[1] Another consequence of this manner of seeing is that one must consider monogamy as favourable to intellectual development, intelligence being a differentiation which accomplishes itself more often, in proportion as there are individuals and groups who differ physically. Physical uniformity engenders uniformity of sensibility, thence of intelligence; this does not need to be explained; now intelligences count, and mark only their differences; uniform, they are as if they were not; impotent to hook themselves one onto the other, to react against each other, lacking asperities, lacking contrary currents. This is the flock, in which each member makes the same gesture of flight, of biting, or of roaring.