NEW YORK — A letter written by Albert Einstein that questions religion is expected to get up to $1.5 million at an auction Tuesday. The so-called "God Letter," written in 1954, will be auctioned by Christie's in New York.

Einstein wrote the letter in German to Eric Gutkind, a philosopher who had written about Jewish spirituality and the pursuit of science. Einstein said that while he "gladly" belonged to the Jewish people, he believed the religion "like all other religions is an incarnation of the most childish superstitions."

This undated photo provided by Christie's shows the first page of Albert Einstein's "God Letter," dated January 3, 1954. AP

"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," he wrote.

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Christie's books and manuscripts specialist Peter Klarnet said the letter is notable for its bluntness.

"Here he is actually quite blunt in what he says," Klarnet said. "The word 'God' is a product of human weakness."

Walter Isaacson, the author of the 2007 biography "Einstein: His Life and Universe," said the great man's views on religion are hard to pin down.

"Einstein generally avoided giving simple answers, and like most human beings his feelings about spirituality varied over time," Isaacson said. "Sometimes he expressed himself in more spiritual terms and sometimes he was more of a debunker of religion."

The letter to Gutkind previously sold for $404,000 at Bloomsbury Auctions in London in 2008.