Commonly attributed to Paine, even on memorials https://commons.wikimedia.org/wiki/File:Thomas_Paine_Plaque_NY.jpg|, and justly describes his ideals, but found nowhere in his writings. It is actually is derived from a quote in Rights of Man: Part 2, "My country is the world, and my religion is to do good."
Misattributed
“My country is the world, and my religion is to do good.”
Part 2.7 Chapter V. Ways and means of improving the condition of Europe, interspersed with miscellaneous observations
Source: 1790s, Rights of Man, Part 2 (1792)
Context: I speak an open and disinterested language, dictated by no passion but that of humanity. To me, who have not only refused offers, because I thought them improper, but have declined rewards I might with reputation have accepted, it is no wonder that meanness and imposition appear disgustful. Independence is my happiness, and I view things as they are, without regard to place or person; my country is the world, and my religion is to do good.
“The world is my country, to promote science is my religion.”
The earliest found citation is in K.O. Meinsma, Spinoza en zijn kring. Historisch-kritische studiën over Hollandsche vrijgeesten (Martinus Nijhoff, 's-Gravenhage, 1896). This influential study was translated in French and German, but not in English. In the original Dutch context it seems as though this is not a quote from Huygens, but a characterisation by the author (Meinsma) of what 'could haven been' Huygens' devise.
In Cosmos: A Personal Voyage (Episode 6) from 1980 it is phrased The world is my country, science my religion.
Also in The Making of Modern Europe, 1648-1780 (1985) by Geoffrey Treasure, p. 474, it is declared that this was Huygens' "motto" — but this seems very similar to the much more famous and long attested declaration of Thomas Paine in Rights of Man (1791): "My country is the world, and my religion is to do good" which has long been paraphrased "The world is my country, and to do good is my religion."
Disputed
“Our Lord Jesus Christ, my brethren, is our hero, a hero all the world wants.”
Sermon (23 November 1879)
Letters, etc
“All I can do is write my stories for mankind, and rest easy.”
Three Times Three (1936)
“My concept of secularism is to be a good human being who respects all religions.”
Quoted in "Sunil Dutt — film star, peace activist, secularist, politician extraordinary" in The Hindu.
We all are one, whichever religion we belong to
“When I do good I feel good, when I do bad I feel bad, and that's my religion.”
Quoted in 3:439 Herndon's Lincoln (1890), p. 439 http://books.google.com/books?id=rywOAAAAIAAJ&pg=PA439&dq=%22when+i+do+good+i+feel+good%22: Inasmuch as he was so often a candidate for public office Mr. Lincoln said as little about his religious code as possible, especially if he failed to coincide with the orthodox world. In illustration of his religious code I once heard him say that it was like that of an old man named Glenn, in Indiana, whom he heard speak at a church meeting, and who said: "When I do good I feel good, when I do bad I feel bad, and that's my religion."
Posthumous attributions
Last will (1809), as quoted in The Fortnightly Review https://books.google.com/books?id=PtlBAQAAMAAJ&pg=PA398&lpg=PA398&dq=%22Let+me+have+none+of+your+Popish+stuff%22&source=bl&ots=XKTgMyyfOF&sig=N-KTteQDfZyKQaQA0yyMGyHkBvU&hl=en&sa=X&ved=0ahUKEwiBhM3xmcrLAhXonIMKHSBLCcoQ6AEIIjAD#v=onepage&q=%22Let%20me%20have%20none%20of%20your%20Popish%20stuff%22&f=false, Volume 31, pp. 398–399
1800s
Source: Memoirs of a Superfluous Man (1943), p. 314
Context: According to my observations, mankind are among the most easily tamable and domesticable of all creatures in the animal world. They are readily reducible to submission, so readily conditionable (to coin a word) as to exhibit an almost incredibly enduring patience under restraint and oppression of the most flagrant character. So far are they from displaying any overweening love of freedom that they show a singular contentment with a condition of servitorship, often showing a curious canine pride in it, and again often simply unaware that they are existing in that condition.
