Carl Edward Sagan (1934-1997) was an astronomer and science popularizer.
In a March 1996 profile by Jim Dawson in the Minneapolis Star-Tribune, Sagan talked about his then-new book The Demon Haunted World and was asked about his personal spiritual views: "My view is that if there is no evidence for it, then forget about it," he said. "An agnostic is somebody who doesn't believe in something until there is evidence for it, so I'm agnostic."
Update from Tom Head, editor of Conversations with Carl Sagan (University Press of Mississippi, 2006):
Sagan resisted the atheism label and self-described as an agnostic.
In a 1981 interview with U.S. Catholic, Sagan said: "I have some discomfort with both believers and with nonbelievers when their opinions are not based on facts ... If we don't know the answer, why are we under so much pressure to make up our minds, to declare our allegiance to one hypothesis or the other?"
In a 1996 interview with NPR's Talk of the Nation, Sagan said (when asked about religious beliefs): "Where's the evidence? Now, the word God is used to cover a wide variety of very different ideas, ranging maybe from the idea of an outsized light-skinned male with a long white beard who sits in a throne in the sky and tallies the fall of every sparrow--for which there is no evidence, none at all--to the view of Einstein, of Spinoza, which is essentially that God is the sum total of the laws of nature. And since there are laws of nature ... if that's what you mean by God, then of course there's a God. So everything depends on the definition of God."
In a 1996 interview with NPR's Fresh Air, Sagan said: "I find that you learn absolutely nothing about someone's belief if yu ask them 'Do you believe in God?' and they say yes or no. You have to specify which of the countless kinds of God you have in mind."
In another 1996 interview, Sagan told Joel Achenbach: "An atheist has to know more than I know. An atheist is someone who knows there is no God."
In an interview with The Humanist magazine conducted after Sagan's death, his wife, Ann Druyan, said that neither she nor Sagan believed in a traditional God or an afterlife.
Carl Sagan has been credited with summarizing many atheists position on the splendor and beauty of the Universe. Diana Nyad was interviewed by Oprah Winfrey on this very issue and it caused an uproar in the atheist community when Oprah misunderstood the atheist position. Atheists have shown that they can see beauty, awe, and wonder. These sometimes overwhelming feelings can come from our inspection of our own existence, the universe, the hubble deep field, a dolphin having homosexual sex, a pyramid in Egypt, or anything else that can be found beautiful in it's own way. Atheists may not all embrace spirituality and this is often because the word has connotations different from the desired usage. You'll be hard pressed to find an atheist that doesn't see awe and wonder at something in this beautiful Universe we have the good fortune of having come into existence in.
As Sagan wrote in "The Demon-Haunted World":
"When we recognize our place in an immensity of light‐years and in the passage of ages, when we grasp the intricacy, beauty and subtlety of life, then that soaring feeling, that sense of elation and humility combined, is surely spiritual.”
Michael Shermer wrote about Carl Sagan in his book "Why Darwin Matters:"
There are many ways to be spiritual, and science is one in its awe-inspiring account about who we are and where we came from. “The cosmos is within us. We are made of star stuff. We are a way for the cosmos to know itself,” began the late astronomer Carl Sagan in the opening scene of Cosmos, filmed just down coast from Esalen, in referring to the stellar origins of the chemical elements of life. “We’ve begun at last to wonder about our origins, star stuff contemplating the stars, organized collections of ten billion billion billion atoms contemplating the evolution of matter, tracing that long path by which it arrived at consciousness … Our obligation to survive and flourish is owed not just to ourselves but also to that cosmos, ancient and vast, from which we spring.”
That is spiritual gold. - Michael Shermer also has posted this online.