The peril in question is the peril of having in a democracy large groups of voters actuated by racial and national affiliations other than those of the country in which they live: in other words, large elements of unassimilated foreigners. The assertion of this danger does not necessarily carry the implication of any inferiority, mental, physical, or moral, on the part of the foreigners. Difference without inferiority is dangerous, difference coupled with inferiority is definitely injurious. There is no need to reiterate the manifold evils which have already developed, and which threaten to develop, from immigration of the poor quality which our selective tests have not sufficed to prevent. Undoubtedly the physical and mental average of our people, possibly also the moral average, has already been definitely reduced, and the progress of the working classes toward a reasonably high standard of living has been checked, but the point which needs emphasis here is that difference in itself is dangerous. The immigrant who is still a foreigner in sympathy and character exerts a prejudicial influence upon the life of the nation at every point of contact. It is impossible for him to function as a normal unit in the social complex. If by naturalization he acquires the right to participate in political affairs, the opportunity for injury is multiplied. He cannot possibly approach public questions as if his allegiance were wholly with the country of his residence. These facts are particularly illustrated with us by the very large element known as "birds of passage." The only way these evils can be overcome is through genuine assimilation. Assimilation is a spiritual metamorphosis. It manifests itself in many changes of dress, of language, of manners, and of conduct. But these outward semblances are not assimilation. An alien is thoroughly assimilated into a new society only when he becomes completely imbued with its spiritual heritage. He must cease to think and feel and imagine in ways determined by his old social environment, and must respond to the stimuli of social contact in all ways exactly as if from the very beginning he had developed under the influence of his adopted society. And this involves, of course, the entire abandonment of any sympathy, affection, or loyalty different from that which might be felt by any native of his new home for the country of his origin or the people of that country. Complete assimilation so defined may seem impossible to the adult immigrant. This is almost universally the truth. The spiritual impress of the environment of one's infancy, childhood, and youth, can seldom be eradicated during the later years of life. Realizing this, those who hate to admit that our immigrants are not being assimilated, hasten to modify the definition. But this does not help the case, because it does not alter the situation.