Lewis compares a Christian's battles with his desires to two other great conflicts--one historical, one literary.
Sherlock Holmes's arch-enemy was Professor Moriarty. He appears or is mentioned in "The Final Problem," The Valley of Fear, "The Empty House," and other Holmes stories. "In 1891 ... [Moriarty] pursued the detective across Europe to the [Reichenbach] Falls in Switzerland, where the two fought and Moriarty fell to his death" (internationalhero.co.uk).
Gilbert Keith Chesterton (1874-1936) was one of the most prolific writers of the twentieth century and was, like Lewis, a Christian. According to the American Chesterton Society, "He wrote a hundred books, contributions to 200 more, hundreds of poems, including the epic Ballad of the White Horse, five plays, five novels, and some two hundred short stories, including a popular series featuring the priest-detective, Father Brown. In spite of his literary accomplishments, he considered himself primarily a journalist. ... Chesterton was equally at ease with literary and social criticism, history, politics, economics, philosophy, and theology. His style is unmistakable, always marked by humility, consistency, paradox, wit, and wonder."
Lewis is referring to statements Chesterton made in "A Defence of Rash Vows," which appears in The Defendant: "The revolt against vows has been carried in our day even to the extent of a revolt against the typical vow of marriage. It is most amusing to listen to the opponents of marriage on this subject. They appear to imagine that the ideal of constancy was a yoke mysteriously imposed on mankind by the devil, instead of being, as it is, a yoke consistently imposed by all lovers on themselves. They have invented a phrase, a phrase that is a black and white contradiction in two words—'free-love'—as if a lover ever had been, or ever could be, free. It is the nature of love to bind itself, and the institution of marriage merely paid the average man the compliment of taking him at his word" (emphasis added).
And Jesus answered them, saying, The hour is come, that the Son of man should be glorified. Verily, verily, I say unto you, Except a corn [i.e., kernel] of wheat fall into the ground and die, it abideth alone: but if it die, it bringeth forth much fruit. He that loveth his life shall lose it; and he that hateth his life in this world shall keep it unto life eternal. If any man serve me, let him follow me; and where I am, there shall also my servant be: if any man serve me, him will my Father honour.
"Throw up the sponge" has the same meaning as today's more common phrase "throw in the towel." As Lewis says, it means to give in, to quit.
According to fun-with-words.com, "In its original form, to throw up the sponge, ... appears in 'The Slang Dictionary' (1860). The reference is to the sponges used to cleanse combatants' faces at prize fights. One contestant's manager throwing in the sponge would signal that as that side had had enough the sponge was no longer required. In recent years, towels have been substituted for sponges at fights, and consequently in the expression too."
Lewis wrote these unintentionally prescient words regarding marriage in 1942. Little did he know that "on April 23, [1956,] he [would enter] into a civil marriage with Joy Davidman at the Oxford Registry Office for the purpose of conferring upon her the status of British citizenship in order to prevent her threatened deportation by British migration authorities" (C. S. Lewis Foundation website) and that on March 21, 1957, the Rev. Peter Bide would go "to the hospital and, at Lewis's request, ... [marry] Lewis and Joy" (Out of My Bone: The Letters of Joy Davidman, p. 310), thus consecrating their vows in the eyes of the Anglican Church.
See the second Bookmark for page 84 for the Scriptural background of this idea.
The command to "love thy neighbour" occurs at least eight times in Scripture.
The horrendous events of World War 2 were, of course, much on Lewis's mind as he wrote Mere Christianity. Here he is referencing Germany's conquering of Poland, which began on September 1, 1939. The cost of the war in terms of human suffering in Poland is almost incomprehensible.
According to www.kasprzyk.demon.co.uk, "Over half a million fighting men and women, and 6 million civilians (or 22% of the total population) died. About 50% of these were Polish Christians and 50% were Polish Jews. Approximately 5,384,000, or 89.9% of Polish war losses (Jews and Gentiles) were the victims of prisons, death camps, raids, executions, annihilation of ghettos, epidemics, starvation, excessive work and ill treatment. So many Poles were sent to concentration camps that virtually every family had someone close to them who had been tortured or murdered there."
And, from wikipedia, "In 1942, the Germans began the systematic killing of the Jews.... Six extermination camps (Auschwitz, Belzec, Chełmno, Majdanek, Sobibór and Treblinka) were established [in Poland] in which the most extreme measure of the Holocaust, the mass murder of millions of Jews from Poland and other countries, was carried out between 1942 and 1944. Of Poland's prewar Jewish population of 3 million, only about 369,000 survived the war."
Lewis may have been thinking of a portion of Hebrews 11 here, which refers to past "heroes of the faith."
Some were tortured, refusing to accept release, so that they might rise again to a better life. Others suffered mocking and flogging, and even chains and imprisonment.They were stoned, they were sawn in two, they were killed with the sword. They went about in skins of sheep and goats, destitute, afflicted, mistreated—of whom the world was not worthy—wandering about in deserts and mountains, and in dens and caves of the earth. (verses 35-38, ESV)
Matthew 6 and Luke 11 ("forgive us our sins, for we ourselves forgive everyone who is indebted to us").
After completing the prayer in Matthew 6, Christ explains, "For if you forgive others their trespasses, your heavenly Father will also forgive you,but if you do not forgive others their trespasses, neither will your Father forgive your trespasses" (verses 14-15).
"Thou shalt not kill" is one of the Ten Commandments given by God to Moses on Mt. Sinai, found in Exodus 20. According to the footnotes in the English Standard Version, "The Hebrew word [for kill] also covers causing human death through carelessness or negligence."
In Luke 3, John the Baptist used strong words when preaching to the crowds who came to hear him, calling them a "brood of vipers" and urging them to repent. Soldiers in the crowd "asked him, 'And we, what shall we do?' And he said to them, 'Do not extort money from anyone by threats or by false accusation, and be content with your wages.'"
And in Luke 7, Christ miraculously heals a Roman centurion's servant and commends the centurion for his faith.
While I don't believe that from a Christian perspective Lewis is wrong in his statements here, I do think his wartime experiences tend to skew his exegesis of Christ's statements about loving one's enemies. Christ was primarily speaking of our personal enemies--people we can't get along with, people who intentionally oppose us and do us wrong--rather than enemies of the state during wartime. Those kinds of enemies--personal enemies--of course, Christians are not justified in killing, as the Bible makes plain (and with which Lewis would unquestionably agree). Quotes below are from the King James Version.
Proverbs 25:21-22: "If thine enemy be hungry, give him bread to eat; and if he be thirsty, give him water to drink: For thou shalt heap coals of fire upon his head, and the LORD shall reward thee."
Matthew 5:21-22: Christ said, "Ye have heard that it was said by them of old time, Thou shalt not kill; and whosoever shall kill shall be in danger of the judgment: But I say unto you, That whosoever is angry with his brother without a cause shall be in danger of the judgment: and whosoever shall say to his brother, Raca [i.e., "Worthless"], shall be in danger of the council: but whosoever shall say, Thou fool, shall be in danger of hell fire."
Matthew 5:38-45: Christ said, "Ye have heard that it hath been said, An eye for an eye, and a tooth for a tooth: But I say unto you, That ye resist not evil: but whosoever shall smite thee on thy right cheek, turn to him the other also. And if any man will sue thee at the law, and take away thy coat, let him have thy cloke also. And whosoever shall compel thee to go a mile, go with him twain. Give to him that asketh thee, and from him that would borrow of thee turn not thou away. Ye have heard that it hath been said, Thou shalt love thy neighbour, and hate thine enemy. But I say unto you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you, and persecute you; That ye may be the children of your Father which is in heaven: for he maketh his sun to rise on the evil and on the good, and sendeth rain on the just and on the unjust."
Luke 6:27-36: Christ said, "But I say unto you which hear, Love your enemies, do good to them which hate you, Bless them that curse you, and pray for them which despitefully use you. And unto him that smiteth thee on the one cheek offer also the other; and him that taketh away thy cloke forbid not to take thy coat also. Give to every man that asketh of thee; and of him that taketh away thy goods ask them not again. And as ye would that men should do to you, do ye also to them likewise. For if ye love them which love you, what thank have ye? for sinners also love those that love them. And if ye do good to them which do good to you, what thank have ye? for sinners also do even the same. And if ye lend to them of whom ye hope to receive, what thank have ye? for sinners also lend to sinners, to receive as much again. But love ye your enemies, and do good, and lend, hoping for nothing again; and your reward shall be great, and ye shall be the children of the Highest: for he is kind unto the unthankful and to the evil. Be ye therefore merciful, as your Father also is merciful."
Lewis is probably thinking of Ezekiel 28:11-19, a passage in which, as most Bible expositors believe, the "king of Tyrus" represents Satan. Quotation below is from the King James Version, emphasis mine.
"Moreover the word of the LORD came unto me, saying, Son of man, take up a lamentation upon the king of Tyrus, and say unto him, Thus saith the Lord GOD; Thou sealest up the sum, full of wisdom, and perfect in beauty. Thou hast been in Eden the garden of God; every precious stone was thy covering, the sardius, topaz, and the diamond, the beryl, the onyx, and the jasper, the sapphire, the emerald, and the carbuncle, and gold: the workmanship of thy tabrets and of thy pipes was prepared in thee in the day that thou wast created. Thou art the anointed cherub that covereth; and I have set thee so: thou wast upon the holy mountain of God; thou hast walked up and down in the midst of the stones of fire. Thou wast perfect in thy ways from the day that thou wast created, till iniquity was found in thee. By the multitude of thy merchandise they have filled the midst of thee with violence, and thou hast sinned: therefore I will cast thee as profane out of the mountain of God: and I will destroy thee, O covering cherub, from the midst of the stones of fire. Thine heart was lifted up because of thy beauty, thou hast corrupted thy wisdom by reason of thy brightness: I will cast thee to the ground, I will lay thee before kings, that they may behold thee. Thou hast defiled thy sanctuaries by the multitude of thine iniquities, by the iniquity of thy traffick; therefore will I bring forth a fire from the midst of thee, it shall devour thee, and I will bring thee to ashes upon the earth in the sight of all them that behold thee. All they that know thee among the people shall be astonished at thee: thou shalt be a terror, and never shalt thou be any more."
And, from Isaiah 14:12-15,
"How art thou fallen from heaven, O Lucifer, son of the morning! how art thou cut down to the ground, which didst weaken the nations! For thou hast said in thine heart, I will ascend into heaven, I will exalt my throne above the stars of God: I will sit also upon the mount of the congregation, in the sides of the north: I will ascend above the heights of the clouds; I will be like the most High. Yet thou shalt be brought down to hell, to the sides of the pit."
Here Lewis references Christ's words in Matthew 7:21-23: "Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven. Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works? And then will I profess unto them, I never knew you: depart from me, ye that work iniquity."
Lewis is referencing Christ's Parable of the Talents, found in Matthew 25:14-30.