“On these occasions I consider how mankind may be connected like one great family in fraternal ties—I endulge a fond, perhaps an enthusiastic idea, that as the world is evidently much less barbarous than it has been, its melioration must still be progressive—that nations are becoming more humanized in their policy—that the subjects of ambition & causes for hostility are daily diminishing—and in fine, that the period is not very remote when the benefits of a liberal & free commerce will, pretty generally, succeed to the devastations & horrors of war.”

Kosmos (1847)
Context: If we would indicate an idea which, throughout the whole course of history, has ever more and more widely extended its empire, or which, more than any other, testifies to the much-contested and still more decidedly misunderstood perfectibility of the whole human race, it is that of establishing our common humanity — of striving to remove the barriers which prejudice and limited views of every kind have erected among men, and to treat all mankind, without reference to religion, nation, or color, as one fraternity, one great community, fitted for the attainment of one object, the unrestrained development of the physical powers. This is the ultimate and highest aim of society, identical with the direction implanted by nature in the mind of man toward the indefinite extension of his existence. He regards the earth in all its limits, and the heavens as far as his eye can scan their bright and starry depths, as inwardly his own, given to him as the objects of his contemplation, and as a field for the development of his energies. Even the child longs to pass the hills or the seas which inclose his narrow home; yet, when his eager steps have borne him beyond those limits, he pines, like the plant, for his native soil; and it is by this touching and beautiful attribute of man — this longing for that which is unknown, and this fond remembrance of that which is lost — that he is spared from an exclusive attachment to the present. Thus deeply rooted in the innermost nature of man, and even enjoined upon him by his highest tendencies, the recognition of the bond of humanity becomes one of the noblest leading principles in the history of mankind.

Christian Missions: A Triangular Debate, Before the Nineteenth Century Club of New York (1895)

An Old Chaos: Humanism and Flying Saucers (p. 75)
The Silence of Animals: On Progress and Other Modern Myths (2013)

Book III, Ch. 9, sec. 4
An Essay Concerning Human Understanding (1689)

Journal entry (11 December 1941); later published in The Wartime Journals (1970)
Context: We talk about spreading democracy and freedom all over the world, but they are to us words rather than conditions. We haven't even got them here in America, and the farther we get into this war the farther we get away from democracy and freedom. Where is it leading us to, and when will it end? The war might stop this winter, but that is improbable. It may go on for fifty years or more. That also is improbable. The elements are too conflicting and confused to form any accurate judgment of its length. There may be a series of wars, one after another, going on indefinitely.
Possibly the world will come to its senses sooner than I expect. But, as I have often said, the environment of human life has changed more rapidly and more extensively in recent years than it has ever changed before. When environment changes, there must be a corresponding change in life. That change must be so great that it is not likely to be completed in a decade or in a generation.

Speech to the press (29 October 1923), quoted in Vakur Versan, 'The Kemalist Reform of Turkish Law and Its Impact', in Jacob M. Landau (ed.), Atatürk and the Modernization of Turkey (Boulder, Colorado: Westview Press, 1984), p. 247

"Outlines of Experiments and Inquiries Respecting Sound and Light" (1800)

Source: Adams-Jefferson Letters

Jón Hreggviðsson
Íslandsklukkan (Iceland's Bell) (1946), Part II: The Fair Maiden