In Iran, under the auspices of President Mahmoud Ahmadinejad, people from around the world have gathered to explore whether or not the Holocaust really happened. The fact that such an event is taking place is mind-numbing. I am a scholar of the history of the Holocaust, and I am also a child and grandchild of Holocaust survivors. My father suffered cold, hunger, disease, despair and gratuitous cruelty as a Jewish slave laborer attached to the Hungarian army during World War II. Some 80 percent of the men who served in units similar to his did not return home from the Eastern Front, to which they were sent simply because they were Jews. My grandmother miraculously survived Auschwitz, a labor camp in Trautenau, and the horrible last weeks of the war in Bergen-Belsen, where tens of thousands of camp inmates were dumped by the Nazis and unceremoniously left to die of starvation and typhus. She lost five of her seven siblings in the Holocaust, including a sister who was with her when she first arrived in Auschwitz, and her sister's daughter, Evie. I can remember as a little boy asking my grandmother about the photograph of a young girl she kept in a box, and being told it was Evie. At the ramp in Auschwitz, where Nazi doctors decided who would be murdered immediately and who would first be made to perform forced labor, my grandmother stood with her sister and her niece. The doctor asked my grandmother, "Who is the mother of the girl?" My grandmother responded ingenuously that she was not. Evie and her mother were sent to their deaths, while my grandmother was spared. Needless to say, the photograph elicited feelings of profound sadness and guilt whenever my grandmother saw it. She always said that if only she had declared that she was the mother, her sister would have lived. Of course, given the Nazis' designs, Evie could not have been saved either way. WORDS ARE inadequate to express the feeling of insult, sacrilege and anger that I feel when Ahmadinejad and his ilk call this history into question. It is my family's history, the history of my people, and the shared history of much of the world. It is also the history that my colleagues and I at Yad Vashem can verify and recount in great detail, based on the 110,000 published titles and the 70 million pages of documentation in our collection, and the personal records of a sizable percentage of the individual Jews who were murdered. It is a history I have shared with countless visitors to Yad Vashem over the years, including presidents and prime ministers. Calling the Holocaust into question can only be likened to questioning if the earth rotates around the sun, or if humans need to breathe to live - but with the addition of a feeling of unfathomable sadness and loss. Debating a Holocaust denier is like debating a person at the beach who swears that the blue-green sea undulating before him is pink. Without doubt, Ahmadinejad thinks differently than we do. For him, historical facts are a matter of opinion, and matters of opinion, such as whether Islam is the "true" religion, are facts. It is crystal-clear that the Western notions of proof and logic are not integral to his way of life, but are only manipulated by him for his own ends. At the upcoming conference in Iran, for certain, the participants will marshal their fallacious evidence to prove their unfounded thesis, eschewing scientific methods for those of pseudo-science and sophistry. DENYING and ridiculing the Holocaust and refusing to comply with international conventions regarding developing nuclear capabilities are merely expressions of the same arrogance, born of ignorance. Ahmadinejad and his crew have amply demonstrated that they will not be swayed by reasonable argument, but will do whatever they want, regardless of the price for mankind. The leaders of the world have yet to find a way to deal with the threat Ahmadinejad poses. The question is: Since words have proven futile, will the world take concerted action before it is too late? The writer is director of the Yad Vashem Libraries, author of Approaching the Holocaust, Texts and Contexts, and co-editor of The Holocaust: Frequently Asked Questions.