Many medical school graduates want to establish lucrative private practices, but for Kevin M. Cahill, M.D., the Bronx-born son of an Irish physician, that was never enough. Instead, Cahill became a leading specialist in tropical medicine, treating victims of famine, violence, war and disease for 45 years in some of the most volatile areas of the globe. He has also become a potent force in humanitarian assistance and international relief efforts as lecturer, teacher, activist, diplomat and advocate, becoming involved in a "major move to alter the ways that America delivers health services abroad." To Bear Witness: A Journey of Healing and Solidarity is an illustrated collection of Cahill's writings from op-ed pieces and essays to speeches and articles documenting the metamorphosis that occurred in his life as he became "immersed in the tragedies of third world countries."Tales of Cahill's humanitarian and medical missions to Lebanon, Somalia, Nicaragua, Libya and Ireland, among other countries, lead to his desire to change the way governments form foreign policies, offering insights often left off the table in political debates, legal arguments and military planning. Cahill speaks movingly about the landmine crisis, "one of the great scourges of history . . . turning vast areas of the earth into wastelands of death, economic ruin and social disintegration." And as the chief medical advisor for Counterterrorism to the New York City Police Department, he offers another perspective on the losses of 9/11; with millions dead of disease and starvation in Somalia and Sudan, nearly a million hacked to death in Rwanda, along with massive human causalities in Armenia, Srebrenica, Congo and Central America over recent decades, "it is important to keep a balance if we are to live in an international world that also knows the constant fear of death and the reality of tragedy."A professional from a privileged nation, Cahill's chosen work has drawn him into a personal relationship with suffering and the inequities experienced by the "downtrodden masses" who survive incredible challenges and have become his "role models in how to live with courage and joy in a harsh but still hopeful world." Deanna Larson is a writer in Nashville.