Albert Einstein: arch rationalist or scientist with a spiritual core? A letter being auctioned in London this week adds more fuel to the long-simmering debate about the Nobel prize-winning physicist's religious views. In the note, written the year before his death, Einstein dismissed the idea of God as the product of human weakness and the Bible as "pretty childish." The letter, handwritten in German, is being sold by Bloomsbury Auctions on Thursday and is expected to fetch from 6,000 to 8,000 pounds (US$12,000 to US$16,000; â‚¬7,500 to â‚¬10,000). Einstein, who helped unravel the mysteries of the universe with his theory of relativity, expressed complex and arguably contradictory views on faith, perceiving a universe suffused with spirituality while rejecting organized religion. The letter up for sale, written to philosopher Eric Gutkind in January 1954, suggests his views on religion did not mellow with age. In it, Einstein said that "the word God is for me nothing more than the expression and product of human weaknesses, the Bible a collection of honorable but still primitive legends which are nevertheless pretty childish." "For me," he added, "the Jewish religion like all other religions is an incarnation of the most childish superstitions." Addressing the idea that the Jews are God's chosen people, Einstein wrote that "the Jewish people to whom I gladly belong and with whose mentality I have a deep affinity have no different quality for me than all other people. As far as my experience goes, they are also no better than other human groups, although they are protected from the worst cancers by a lack of power. Otherwise I cannot see anything 'chosen' about them." Bloomsbury spokesman Richard Caton said the auction house was "100 percent certain" of the letter's authenticity. It is being offered at auction for the first time, by a private vendor. John Brooke, emeritus professor of science and religion at Oxford University, said the letter lends weight to the notion that "Einstein was not a conventional theist" - although he was not an atheist, either. "Like many great scientists of the past, he is rather quirky about religion, and not always consistent from one period to another," Brooke said. Born to a Jewish family in Germany in 1879, Einstein said he went through a devout phase as a child before beginning to question conventional religion at the age of 12. In later life, he expressed a sense of wonder at the universe and its mysteries - what he called a "cosmic religious feeling" - and famously said: "Science without religion is lame, religion without science is blind." But, he also said: "I do not believe in the God of theology who rewards good and punishes evil. My God created laws that take care of that. His universe is not ruled by wishful thinking, but by immutable laws." Brooke said Einstein believed that "there is some kind of intelligence working its way through nature. But it is certainly not a conventional Christian or Judaic religious view." Einstein's most famous legacy is the special theory of relativity, which makes the point that a large amount of energy could be released from a tiny amount of matter, as expressed in the equation EMC2 (energy equals mass times the speed of light squared). The theory changed the face of physics, allowing scientists to make predictions about space and paving the way for nuclear power and the atomic bomb. Einstein's musings on science, war, peace and God helped make him world famous, and his scientific legacy prompted Time magazine to name him its Person of the 20th Century.