“It might prove a great encouragement to manumission in the southern parts of the U. S. and even afford the best hope yet presented of putting an end to the slavery, in which not less than 600,000 unhappy Negroes are now involved…”

1860s, Our Composite Nationality (1869)
Context: Southern gentlemen who led in the late rebellion have not parted with their convictions at this point, any more than at any other. They want to be independent of the negro. They believed in slavery and they believe in it still. They believed in an aristocratic class, and they believe in it still, and though they have lost slavery, one element essential to such a class, they still have two important conditions to the reconstruction of that class. They have intelligence, and they have land. Of these, the land is the more important. They cling to it with all the tenacity of a cherished superstition. They will neither sell to the negro, nor let the carpet-bagger have it in peace, but are determined to hold it for themselves and their children forever. They have not yet learned that when a principle is gone, the incident must go also; that what was wise and proper under slavery is foolish and mischievous in a state of general liberty; that the old bottles are worthless when the new wine has come; but they have found that land is a doubtful benefit, where there're no hands to till it. Hence these gentlemen have turned their attention to the Celestial Empire. They would rather have laborers who would work for nothing; but as they cannot get the negro on these terms, they want Chinamen, who, they hope, will work for next to nothing.

1920s, The Progress of a People (1924)
Context: In such a view of the history of the Negro race in America, we may find the evidences that the black man's probation on this continent was a necessary part in a great plan by which the race was to be saved to the world for a service which we are now able to vision and, even if yet somewhat dimly, to appreciate. The destiny of the great African continent, to be added at length — and in a future not now far beyond us — to the realms of the highest civilization, has become apparent within a very few decades. But for the strange and long inscrutable purpose which in the ordering of human affairs subjected a part of the black race to the ordeal of slavery, that race might have been assigned to the tragic fate which has befallen many aboriginal peoples when brought into conflict with more advanced communities. Instead, we are able now to be confident that this race is to be preserved for a great and useful work. If some of its members have suffered, if some have been denied, if some have been sacrificed, we are able at last to realize that their sacrifices were borne in a great cause. They gave vicariously, that a vastly greater number might be preserved and benefited through them. The salvation of a race, the destiny of a continent, were bought at the price of these sacrifices.

Both American and British abolitionists assumed that an end to slave imports would lead automatically to the amelioration and gradual abolition of slavery.
The Problem of Slavery in the Age of Revolution, 1770-1823, page 129. https://books.google.com/books?id=9lsvDwAAQBAJ&pg=PA129

2010s, Interview with the Reuters War College (April 2017)

CNN obituary (17 October 1997) http://www.cnn.com/US/9710/16/michener.obit/

Source: How Europe Underdeveloped Africa (1972), p. 136.

As quoted in "Guardians Of The Galaxy Is Marvel’s Best Movie Yet" by Gregory Wakeman in YAHOO movies (23 July 2014) https://uk.movies.yahoo.com/guardians-galaxy-marvel-best-movie-yet-030700879.html
Context: Just came from the premiere of Guardians of the Galaxy. With all the hype I expected to be a bit disappointed. It just couldn't be as good as everyone was predicting. And they were wrong. It's even better than everyone said. It just might be Marvel's best movie yet.

Source: 1990s, For Cause and Comrades: Why Men Fought in the Civil War (1997), pp. 109–110
Context: It would be wrong, however, to assume that Confederate soldiers were constantly preoccupied with this matter. In fact, only 20 percent of the sample of 429 Southern soldiers explicitly voiced proslavery convictions in their letters or diaries. As one might expect, a much higher percentage of soldiers from slaveholding families than from nonslaveholding families expressed such a purpose: 33 percent, compared with 12 percent. Ironically, the proportion of Union soldiers who wrote about the slavery question was greater, as the next chapter will show. There is a ready explanation for this apparent paradox. Emancipation was a salient issue for Union soldiers because it was controversial. Slavery was less salient for most Confederate soldiers because it was not controversial. They took slavery for granted as one of the Southern 'rights' and institutions for which they fought, and did not feel compelled to discuss it. Although only 20 percent of the soldiers avowed explicit proslavery purposes in their letters and diaries, none at all dissented from that view. But even those who owned slaves and fought consciously to defend the institution preferred to discourse upon liberty, rights, and the horrors of subjugation.