In 1988, the American historian Arno J. Mayer published a book entitled "Why Did the Heavens Not Darken?", which did not explicitly deny the Holocaust, but according to Lucy Dawidowicz lent support to Holocaust denial by stating that most people who died at Auschwitz were the victims of "natural causes" such as disease, not gassing. Dawidowicz argued that Mayer's statements about Auschwitz were "a breathtaking assertion". Holocaust historian Robert Jan van Pelt has written that Mayer's book is as close as a mainstream historian has ever come to supporting Holocaust denial. Holocaust deniers such as David Irving have often cited Mayer's book as one reason for embracing Holocaust denial. Though Mayer has been often condemned for his statement about the reasons for the Auschwitz death toll, his book does not deny the use of gas chambers at Auschwitz, as Holocaust deniers often claim.