Mere Christianity is CS Lewis&39;s forceful and accessible doctrine of Christian belief First heard as informal radio broadcasts and then published as three separate books - The Case for Christianity, Christian Behavior, and Beyond Personality - Mere Christianity brings together what Lewis saw as the funda the boundaries that divide Christianity&39;s round on which all those who have Christian faith can stand together, proving that "at the centre of each there is soences of belief, all differences of temperament, all memories of mutual persecution, speaks the same voice"