Sourced

• von Humboldt (seeing a newspaper containing slanderous falsehoods against Jefferson on the President's desk) : Why do you not have the fellow hung who dares to write these abominable lies?
  Jefferson : What! hang the guardians of the public morals? No, sir, — rather would I protect the spirit of freedom which dictates even that degree of abuse. Put that paper into your pocket, my good friend, carry it with you to Europe, and when you hear any one doubt the reality of American freedom, show them that paper, and tell them where you found it.
  Humboldt : But is it not shocking that virtuous characters should be defamed?
  Jefferson : Let their actions refute such libels. Believe me, virtue is not long darkened by the clouds of calumny; and the temporary pain which it causes is infinitely overweighed by the safety it insures against degeneracy in the principles and conduct of public functionaries. When a man assumes a public trust, he should consider himself as public property.
  • Conversation reported in B.L. Rayner, Life of Jefferson (1834), p. 356. The exact date is not known, but the conversation took place in one of several meetings with the President during Humboldt's visit to Washington, D.C., from June 1 to June 27, 1804.

Equinoctial Regions of America (1814-1829)

• Devoted from my earliest youth to the study of nature, feeling with enthusiasm the wild beauties of a country guarded by mountains and shaded by ancient forests, I experienced in my travels, enjoyments which have amply compensated for the privations inseparable from a laborious and often agitated life.

• One of the noblest characteristics which distinguish modern civilization from that of remoter times is, that it has enlarged the mass of our conceptions, rendered us more capable of perceiving the connection between the physical and intellectual world, and thrown a more general interest over objects which heretofore occupied only a few scientific men, because those objects were contemplated separately, and from a narrower point of view.

• The expression of vanity and self-love becomes less offensive, when it retains something of simplicity and frankness.

• Our imagination is struck only by what is great; but the lover of natural philosophy should reflect equally on little things.

• In order to ameliorate without commotion new institutions must be made, as it were, to rise out of those which the barbarism of centuries has consecrated. It will one day seem incredible that until the year 1826 there existed no law in the Great Antilles to prevent the sale of young infants and their separation from their parents, or to prohibit the degrading custom of marking the negroes with a hot iron, merely to enable these human cattle to be more easily recognized.

Kosmos (1845 - 1847)

• The principal impulse by which I was directed was the earnest endeavor to comprehend the phenomena of physical objects in their general connection, and to represent nature as one great whole, moved and animated by internal forces. My intercourse with highly-gifted men early led me to discover that, without an earnest striving to attain to a knowledge of special branches of study, all attempts to give a grand and general view of the universe would be nothing more than a vain illusion. These special departments in the great domain of natural science are, moreover, capable of being reciprocally fructified by means of the appropriative forces by which they are endowed.

• While we maintain the unity of the human species, we at the same time repel the depressing assumption of superior and inferior races of men. There are nations more susceptible of cultivation, more highly civilized, more enobled by mental cultivation than others, but none in themselves nobler than others. All are in like degree designed for freedom; a freedom which, in the ruder conditions of society, belongs only to the individual, but which, in social states enjoying political institutions, appertains as a right to the whole body of the community.

• From the remotest nebulæ and from the revolving double stars, we have descended to the minutest organisms of animal creation, whether manifested in the depths of ocean or on the surface of our globe, and to the delicate vegetable germs which clothe the naked declivity of the ice-crowned mountain summit; and here we have been able to arrange these phenomena according to partially known laws; but other laws of a more mysterious nature rule the higher spheres of the organic world, in which is comprised the human species in all its varied conformation, its creative intellectual power, and the languages to which it has given existence. A physical delineation of nature terminates at the point where the sphere of intellect begins, and a new world of mind is opened to our view. It marks the limit, but does not pass it.

• The most powerful influence exercised by the Arabs on general natural physics was that directed to the advances of chemistry; a science for which this race created a new era.(...) Besides making laudatory mention of that which we owe to the natural science of the Arabs in both the terrestrial and celestial spheres, we must likewise allude to their contributions in separate paths of intellectual development to the general mass of mathematical science.
  • Cosmos, H.G. Bohn, 1860, v2, p.589,595

Attributed

• Cruelty to animals is one of the most significant vices of a low and ignoble people. Wherever one notices them, they constitute a sure sign of ignorance and brutality which cannot be painted over even by all the evidence of wealth and luxury. Cruelty to animals cannot exist together with true education and true learning.

• Only what we have wrought into our character during life can we take away with us.