The Nonfiction of Robert Heinlein Volume I.
The excerpt is from 1952 and it was for Edward R. Murrow's radio show "This I Believe".
"...I believe that for every coward there are countless unknown heroes. I believe in Rodger Young. I am safe today because of endless, unnamed heroes from Valley Forge to the Yalu River.
I believe in—I am proud to belong to—the United States. Despite its shortcomings, from lynchings to bad faith in high places, I believe that this our nation has and has had the most decent and kindly internal practices and foreign policies to be found anywhere in history.
And finally, I believe in my whole race, yellow, white, black, red, brown—in the honesty, courage, intelligence, durability ...and goodness...of the overwhelming majority of my brothers and sisters everywhere on this planet. I am proud to be a human being. I believe that we have come this far by
the skin of our teeth, that we will always make it just by the skin of our teeth—but that we will always make it, survive...endure. I believe that this hairless embryo with the aching, oversize braincase and the opposable thumb, this animal barely up from the apes, will endure—will endure longer than his home planet, will spread out to the other planets, to the stars, and beyond, carrying with him his honesty, his unlimited courage—and his noble essential decency. This I believe with all my heart."