On Monday afternoon an explosive device was delivered to my father’s home north of New York City. An alert member of our staff recognized the threat and called the police. Fortunately, the authorities were able to detonate the device safely. On Wednesday, the Secret Service said it had intercepted similar devices sent to the offices of former President Barack Obama and former Secretary of State Hillary Clinton.

We are all grateful that no one was injured, and grateful to those who kept us safe. But the incident was profoundly disturbing — as a threat not just to the safety of our family, neighbors, colleagues and friends, but also to the future of American democracy.

My family is no stranger to the hostilities of those who reject our philosophy, our politics and our very identity. My father grew up in the shadow of the Nazi regime in Hungary. My grandfather secured papers with false names so that they could survive the onslaught against Budapest’s Jews; he helped many others do the same. After the war, as the Communists took power, my father escaped to London, where he studied at the London School of Economics before embarking on what ultimately became a hugely successful career in finance.

But the lessons of his early life never left him. His biggest philanthropic endeavor, the Open Society Foundations, played a leading role in supporting the transition from Communism to more democratic societies in parts of the former Soviet Union and then expanded to protect democratic practices in existing democracies. My father acknowledges that his philanthropic work, while nonpartisan, is “political” in a broad sense: It seeks to support those who promote societies where everyone has a voice.