Positive Eugenics is the science of race building through wise mating. "As long as ability marries ability, a large proportion of able offspring is a certainty."[11] What prospective parent does not fondly imagine that his children will be at least near-great? Yet how many individuals, in their choice of a mate, set out with the deliberate intention of securing a life partner whose qualities, when combined with his own, must produce greatness? The Darwin-Galton-Wedgwood families boast sixteen men of world fame in five generations; in the Bach family there were fifty-seven musicians of note in eight generations; Wood's study of _Heredity in Royalty_ shows the evident transmission of special ability; yet men and women of ability, anxious for able offspring, mate without any rational effort to secure the end which they desire. "Ninety-nine times out of a hundred our mathematician marries a woman whose family did not count a single astronomer, physicist or other mathematical mind among it members. The result of such a union is what could be expected. Although genius does not generally die out right away in the first generation, it decreases by half, and further dilutions soon bring it down to nothingness."[12] This, in brief, is the problem of Negative and of Positive Eugenics. Both defect and ability are transmitted by heredity; both are the product of the mating process known as marriage; since society can and does control marriage, it may, through this control, exercise a real influence upon the character of future generations. The science of Eugenics is in its infancy, yet, widely established and vigorously applied, it may revolutionize the human species. The Super Race may come, because "looked at from the social standpoint, we see how exceptional families, by careful marriages, can within even a few generations, obtain an exceptional stock, and how directly this suggests assortative mating as a moral duty for the highly endowed. On the other hand, the exceptionally degenerate isolated in the slums of our modern cities can easily produce permanent stock also: a stock which no change of environment will permanently elevate, and which nothing but mixture with better blood will improve. But this is an improvement of the bad by a social waste of the better. We do not want to eliminate bad stock by watering it with good, but by placing it under conditions where it is relatively or absolutely infertile."[13]