We had, four or five weeks ago, a few words of controversy with the _Christian Union_ as to the comparative morality of the Prussians and Americans, or, rather, their comparative religiousness--meaning by religiousness a disposition "to serve others and live as in God's sight;" in other words, unselfishness and spirituality. We let it drop, from the feeling that the question whether the Americans or Prussians were the better men was only a part, and a very small part, of the larger question. How do we discover which of any two nations is the purer in its life or in its aims? and, is not any judgment we form about it likely to be very defective, owing to the inevitable incompleteness of our premises? We are not now going to try to fix the place of either Prussia or the United States in the scale of morality, but to point out some reasons why all comparisons between them should be made by Americans with exceeding care and humility. There is hardly any field of inquiry in which even the best-informed man is likely to fall into so many errors; first, because there is no field in which the vision is so much affected by prejudices of education and custom; and, secondly, because there is none in which the things we see are so likely to create erroneous impressions about the things we do not see. But we may add that it is a field which no intelligent and sensible man ever explores without finding his charity greatly stimulated. Let us give some illustrations of the errors into which people are apt to fall in it. Count Gasparin, a French Protestant, and as spiritually minded a man as breathed, once talking with an American friend expressed in strong terms his sense of the pain it caused him that Mr. Lincoln should have been at the theatre when he was killed, not, the friend found, because he objected in the least to theatre-going, but because it was the evening of Good Friday--a day which the Continental Calvinists "keep" with great solemnity, but to which American non-episcopal Protestants pay no attention whatever. Count Gasparin, on the other hand, would have no hesitation in taking a ride on Sunday, or going to a public promenade after church hours, and, from seeing him there, his American friend would draw deductions just as unfavorable to the Count's religious character as the Count himself drew with regard to Mr. Lincoln's.