Three short months ago, I received an encouraging text from my friend Ravi Zacharias. Now, as if in a blink of an eye, he has passed away. Along with countless thousands, I grieve. When he wrote, he was reeling from excruciating back pain but wholly unaware of the cancer diagnosis that would soon follow. Despite his suffering and his onerous schedule, he shared that he was praying for my brother, Rush, who had just been diagnosed with cancer. Ravi was a unique Christian apologist and evangelist -- a giant in his field. No one presented the Gospel more cogently and...