Although popular in his own day, C.S. Lewis has e even more influential since his death in 1963. One of the most enduring of Lewis’s works is his book Mere Christianity, which started out as a series of radio lectures that aired on the BBC during World War II.
A YouTube channel called CSLewisDoodle contains a number of videos that illustrate some of Lewis’s selected essays to make them easier to understand. The video below is from the third radio talk (Chapter 4 of Mere Christianity) in which Lewis explains what lies behind the moral law.