Four previously undiscovered letters written and signed by the Nobel Prize winning physicist Albert Einstein (1879-1955), which have never been offered for sale before, are auctioning online at PFC Auctions.
The letters not only tell us a great deal about the beliefs of the man who wrote them, but about the political climate that coloured America following world war two.
The unique collection of letters was addressed to socialist philosopher Corliss Lamont, who was accused of being "un-American" by Senator Joseph McCarthy when he suggested that he felt an affinity with the communist policies of the Soviet Union.
McCarthy's (often unfounded) accusations of communism during the period are now legendary. Many individuals suffered loss of employment, destruction of careers and even imprisonment on the back of such allegations. The term "McCarthyism" is now used more generally to describe reckless, unsubstantiated accusations.
Einstein is supportive of Lamont's beliefs throughout the 1954 correspondence, telling Lamont, who acted as the chairman of the National Council for American-Soviet Friendship, that he had "rendered the country an important service" in January 1954.
Einstein, who moved to the US during the 1930s, continues: "There is one point in your statement which I regretted.
"It is your declaration that you have never been a member of the Communist party. For party membership is a thing about which no citizen has any obligation to give an accounting for."
The letters, which were discovered in a yard sale, shine a light on Einstein's nuanced political beliefs and the supportive role he played throughout Lamont's trial for contempt of Congress - of which he was eventually acquitted.
They are also deeply suggestive of the climate of suspicion and paranoia that defined the age through which the men lived - at its height, the cold war created a backdrop for accusations of subversion or treason without proper regard for evidence, as dramatised in Arthur Miller's The Crucible.
Einstein's missives have proved popular with collectors in the past. In October 2012, a 1954 letter in which Einstein shares his thoughts about God reportedly sold for $3m on eBay.
Adrian Roose of PFC Auctions comments: "It is a unique collection. McCarthy once labelled Einstein an enemy of America.
"Einstein risked his reputation in order to stand up for his political beliefs."
Bidding ends tomorrow (February 28).
Sign up for our free weekly newsletter.