Mere Christianity reveals the fundamental principles of Christianity that are common to all churches. The book is considered a classic of Christian apologetics." The contents of this book were the subject of a series of radio broadcasts and were subsequently published in three separate parts entitled Radio Conversations (1942), Christian Conduct (1943), and Beyond personality" (1944). In the printed version, I made a few additions to what I said into the microphone, but otherwise left the text without any significant changes. A conversation on the radio should not, in my opinion, sound like a literary essay read aloud; it should to be a conversation filled with sincerity. Therefore, in my conversations I used all the abbreviations and colloquial expressions that I usually use in a conversation K.S.L."