Stephen Hawking, the groundbreaking theoretical physicist and cosmologist who died Wednesday at age 76, was an atheist who none-the-less sparked debate about God and religion with his books.

Although he lived more than five decades with a motor neuron disease that usually kills people within three years, he saw no miracles and to the end, he thought heaven was “a fairy story.”

In his 1988 book, A Brief History of Time, which spent 147 weeks on the New York Times bestseller list, he said if we ever understood why the universe exists, “It would be the ultimate triumph of human reason — for then, we would know the mind of God.” Later, however, he told a journalist for El Mundo he meant, “We would know everything God would know if there were a God, which there isn’t. I’m an atheist.”

Hawking’s last science book,The Grand Design, (with physicist Leonard Mlodinow), published in 2010 and a New York Times and Publishers Weekly bestseller, discussed the most current theories of the origins of this universe – and many other universes. Hawking began by saying that current scientific theories predict “a great many universes were created out of nothing. Their creation does not require the intervention of some supernatural being or god. Rather these multiple universes arise naturally from physical law.”

And he concluded it by tossing off God: “Spontaneous creation is the reason there is something rather than nothing, why the universe exists, why we exist. It is not necessary to invoke God to light the blue touch paper and set the universe going.”

Some Christians argued right back.

Popular apologetics author Lee Strobel, in Case for a Creator, interviewed believers who disputed Hawking and concluded the intelligent designer has to have been a supernatural force — God.

In 2011, Oxford Mathematician and evangelical Christian John Lennox’s book God and Stephen Hawking: Whose Design is it Anyway argued that Hawking’s “inadequate idea of God” position only makes God more, not less, probable.

But one of the most famous popularizers of cosmology, Neil deGrasse Tyson, who calls himself an agnostic, wrote in Death by Black Hole, a 2006 collection of science essays: “So you’re made of detritus [from exploded stars]. Get over it. Or better yet, celebrate it. After all, what nobler thought can one cherish than that the universe lives within us all?”