Mere Christianity is a book that Lewis wrote to bring people to Christianity by logic rather than discussing all kinds of religious doctrines. He states basic beliefs about Christianity in general, rather than trying to bring people to a specific denomination of Christianity. Just because this book is meant to bring others to Christianity does not mean the it does not hold important things for us to learn about. He wrote about how once one is brought to Christianity, he waits in a hallway with many doors. Christians try these many doors to the different denominations to see which one fits best with their beliefs.
I agree with Lewis that we cannot judge on which denomination in the true church because there is no perfect denomination on this earth because it is filled with sin. We must look for the church that is closest to the truth. The marks of the true Church are the following: the true preaching of the gospel, the proper administration of the sacraments, and the exercise of Christian discipline (Belgic Confession, Art. 29). The denomination that I have found to be closest to these three marks is the Protestant Reformed Church, of which I am a confessing member. I do not believe this is the only true church, but I believe that by going there I can best glorify God and grow in my faith.
Although we are called to join ourselves to the true church, we are not called to separate ourselves from others from our denomination. Just like cancer cells, if we stop communicating with our neighbors from other churches, we will spread apart and cause more damage than good. Christ wants His church to be united in the truth, and he gathers His Church from all nations of the world. We need to work out our differences using scripture, rather than cutting others who believe differently out of our lives.
I disagree with Lewis when he says that there are no such things as good and bad impulses. I disagree because even when someone’s impulse is to kill a father who beats his child, this is wrong because Jesus says, “Whosoever hateth his brother is a murderer: and ye know that no murderer hath eternal life abiding in him” (I John 3:15). This verse shows that the desire to murder is just as bad as murder.
Even though I disagreed with Lewis about his denial of good and bad impulses, I did agree with him about how people have lessened the meaning of the word Christian. Just as people now use the word gentleman a term of praise, so people use the word Christian to describe anyone they think is a good man. Because it is so often used in a wrong way, it will speedily become a useless word. We must live our lives as thankful people of God to show what the term Christian really