The United States welcomes now, as it has welcomed from the foundation of its government, the voluntary immigration of all aliens coming hither under conditions fitting them to become merged in the body-politic of this land. Our laws provide the means for them to become incorporated indistinguishably in the mass of citizens, and prescribe their absolute equality with the native born, guaranteeing to them equal civil rights at home and equal protection abroad. The conditions are few, looking to their coming as free agents, so circumstanced physically and morally as to supply the healthful and intelligent material of free citizenhood. The pauper, the criminal, the contagiously or incurably diseased, are excluded from the benefits of immigration only when they are likely to become a source of danger or a burden upon the community. The voluntary character of their coming is essential,--hence we shut out all immigration assisted or constrained by foreign agencies. The purpose of our generous treatment of the alien immigrant is to benefit us and him alike,--not to afford to another State a field upon which to cast its own objectionable elements. A convention of naturalization may not be construed as an instrument to facilitate any such process. The alien, coming hither voluntarily and prepared to take upon himself the preparatory, and in due course the definite obligations of citizenship, retains thereafter, in domestic and international relations, the initial character of free agency, in the full enjoyment of which it is incumbent upon his adoptive State to protect him. The foregoing considerations, whilst pertinent to the examination of the purpose and scope of a naturalization treaty, have a larger aim. It behoves the State to scrutinize most jealously the character of the immigration from a foreign land, and, if it be obnoxious to objection, to examine the causes which render it so. Should those causes originate in the act of another sovereign State, to the detriment of its neighbors, it is the prerogative of an injured State to point out the evil and to make remonstrance; for with nations, as with individuals, the social law holds good that the right of each is bounded by the right of the neighbor.