Peter Kreeft is a deep thinker, but has a gift for summarizing complex arguments in an easy-to-understand manner. This video is an excellent response to the argument that the presence of evil in this world disproves the existence of God. On the contrary, he argues, we cannot judge anything as evil without presupposing an objective moral standard, i.e., God.
[Updated Jan. 25, 2016 with link to new video location.]