(2) But this underlying physical attraction, however keen at first is not of guaranteed permanence; it must be buttressed by common tastes and sympathies. To like the same people, to enjoy doing the same things, to judge problems from the same angle, to cleave to similar moral, aesthetic, religious canons is of great importance. A certain amount of contrast in ideas and ideals is, indeed, piquant and stimulating; and where marriage is early there is likelihood of an adequate convergence in Weltanschauung. But too radically different an outlook upon life may lead to continual friction, to loneliness, and mutual antagonism. The two who are to be comrades in the great experiment of life must be able to help each other, strengthen each other's weaknesses, and admire each other's aims and achievements. In particular, religious fanaticism is an intractable enemy of marital happiness. As Stevenson puts it, "There are differences which no habit nor affection can reconcile, and the Bohemian must not ntermarry with the Pharisee. The best of men and the best of women may sometimes live together all their lives, and, for want of some consent on fundamental questions, hold each other lost spirits to the end." (3) It scarcely needs to be added that there must be on both sides a high standard of morality. Truthfulness, sincerity, self-control, the willingness to work, to sacrifice personal desires and pull together for the common welfare of the house, are essential, as well as fidelity to marriage vows and abstinence from all intemperance and lawbreaking. Common tastes can be formed after marriage; even the organic attraction is pretty sure to be awakened in some degree if the pair are not actually repulsive to each other; but low moral ideals at the age of marriage are seldom radically transformed afterward and render any happiness in home-making insecure. (4) Perhaps some day it may become incumbent upon the suitor to weigh the matter of the heredity back of the lady of his choice, and consider whether she is best adapted, by mating with him, to give birth to normal and healthy children; or for the maiden sought to regard with equal care the antecedents of the suitor. But-fortunately for lovers' consciences-we know too little at present about heredity and the breeding of human beings to give much useful advice or make any demands of the prospective couple, except to insist that those who are tainted with hereditary disease or feeble-mindedness shall refrain from marriage. To this subject we shall recur in chapter XXX. Is divorce morally justifiable?