that it has been put in a wrong setting and is therefore capable of a different interpretation than that which its author gives. The difficulty in applying biological principles to sociological problems is so great that any slight error leads to radically false results. Social thinkers must use biology, but care must be taken not to isolate some one principle from related doctrines which if properly presented would vitiate the reasoning drawn from a narrow field. The qualities of mothers are inherited by sons and those of fathers by their daughters, so that if there are any special sex characters they would soon appear in persons of the opposite sex. We are thus intermediate forms with characters coming both from our fathers and mothers. But it does not follow from this that sexual affinity is due to this mixture: for this would assume that we have a special liking for qualities absent in ourselves. On the contrary, we like those like ourselves and have an aversion to those who present differences no matter how slight.
The doctrine of sexual affinity should be so restricted that it will conform to sociological and psychological laws as well as to those of biology. This can be done by keeping in mind a distinction that Weininger has overlooked. Were all characters natural and none acquired, we might assume that they were male or female. But acquired characters can not thus be divided. They are carried along by a social heredity which impresses its effects on both sexes alike. Weininger assumes, however, that all characters are due to differences in germ cells and that every one in his development reveals the tendencies active in them. These tendencies, however, are thwarted by adverse conditions, so that each individual at maturity is either far short of his full development or has been pressed in other directions than forces of the original germ cell would dictate. Differences between men are thus due not merely to variations in germ cells, but to defects which arise out of bad conditions. Persons with the same germ cells may differ more radically at maturity than they differ from those whose germ cells represent some variation in the species. Food, housing, light, air and disease are of prime importance in creating the peculiarities which appear at maturity. The modifications which culminate in some variations of the racial type are in any age too slight to be of importance in accounting for the marked differences which appear in mature men and women. These differences are defects due to bad conditions, not peculiarities of germ cells. They represent retardations in development, not modification of the racial type. We are all short some characters which our heredity would reveal if conditions favored and these shortages are of such infinite variety that scarcely two individuals are alike.
It is generally admitted that improvements in the human race can be made by crosses increasing the number of natural characters. But