Kathleen Lonsdale was a groundbreaking chemist who was instrumental in developing the science of crystallography. She was also a midlife convert to Quakerism who campaigned for peace and prison reform. Horrified by the dropping of the first atomic bombs, Lonsdale felt that the entire scientific community was now tainted by the violence it had enabled. Published in 1957, Is Peace Possible? was her attempt to make amends for this communal guilt by demonstrating that science can bring peace as well as war, and can address the 'big questions' generally left to the humanities. In crystalline language and logic honed from a lifetime of relying on the sharpness of her mind to cut through barriers of class and gender, Kathleen Lonsdale's Is Peace Possible? is a work of quiet, elegant sanity that refuses to be bullied by the received wisdom of war's inevitability. It is a snapshot of a particular moment in history, but its themes are eternally relevant, and even more necessary now than when it was written.