“I think that one of our most important tasks is to convince others that there's nothing to fear in difference; that difference, in fact, is one of the healthiest and most invigorating of human characteristics without which life would become meaningless.”

Source: The Ape that Kicked the Hornet's Nest (2013), p. 267

2016, Young Leaders of the Americas Initiative Town Hall (March 2016)
Context: And I think one of the things that's important for bringing about further progress is that we listen to each other and we understand our differences. I don't think it's necessary for us to all speak one language, or all have the same foods, or all have the same customs. But I do believe that there are some universal principles that are important. I believe that the most important principle is a very simple one that is at the heart of most of the world’s great religions, which is treat somebody the same way you’d want to be treated. And if you start with that basic premise, then we will continue to make progress. But I also think that in order for us to make progress, we have to have that fellow feeling and we have to combine that with the use of our brains and reason, and our intellect. […] That requires not just a strong heart, but also using our heads. And if we do those two things, then I feel confident that we'll make progress.

Source: THE VALUE OF HUMAN DIGNITY: Brunello Cucinelli’s Vision for a Better World https://gearpatrol.com/2018/12/20/brunello-cucinelli-interview/ John Zientek, Gear Patrol, December 20, 2018

Letter Seven (14 May 1904)
Letters to a Young Poet (1934)
Variant: For one human being to love another human being: that is perhaps the most difficult task that has been given to us, the ultimate, the final problem and proof, the work for which all other work is merely preparation.
Source: The Selected Poetry of Rainer Maria Rilke
Context: People have (with the help of conventions) oriented all their solutions toward the easy and toward the easiest side of the easy; but it is clear that we must hold to what is difficult; everything alive holds to it, everything in Nature grows and defends itself in its own way and is characteristically and spontaneously itself, seeks at all costs to be so and against all opposition. We know little, but that we must hold to what is difficult is a certainty that will not forsake us; it is good to be solitary, for solitude is difficult; that something is difficult must be a reason the more for us to do it.
To love is good, too: love being difficult. For one human being to love another: that is perhaps the most difficult of all our tasks, the ultimate, the last test and proof, the work for which all other work is but preparation.

Concerning his affair with Edwina Currie http://news.bbc.co.uk/2/hi/uk_news/politics/2286008.stm.
1990s, 1997

Source: Abortion: The Clash of Absolutes (1990), Approaching Abortion Anew

Vol. 1, bk. 1, ch. 2
Enquiry Concerning Political Justice (1793)

2017, Farewell Address (January 2017)
Context: It falls to each of us to be those anxious, jealous guardians of our democracy; to embrace the joyous task we've been given to continually try to improve this great nation of ours. Because for all our outward differences, we, in fact, all share the same proud title, the most important office in a democracy: Citizen. Citizen.