Here are Lewis's basic arguments and my responses.
We can't know that pacifism produces better results than a just war.
It is true that we can't prove whether pacifism or war does more good. It's obvious that if everyone were pacifists, the world would be a much better place. But since that is an unattainable ideal, the question is rather dealing with whether or not pacifism is better in a world where aggressors and evil abound. We couldn't even get Christian Europe to restrain itself from war for more than a year or two at a time, so how could we ever put pacifism on a large scale to the test? The question is unanswerable in this regard.
But I don't need to answer this question as a Christian. I think Lewis misses a glaring issue in his theology here. It doesn't matter whether pacifism produces "better" results, if by "better" we mean less deaths, less dictatorships, less suffering, etc. As a Christian, that's not my concern. That's God's concern. He can protect, mete out justice, and do whatever he wants to do in his world through the powers that be. My question must be "what are the means God has given me to live life and share the gospel?" Jesus Christ told me I would suffer, be persecuted, and bear my cross if I am a true follower of him. Pragmatism is not my metric for deciding whether or not a moral action is good.
Pacifism means "doing nothing."
Lewis feels that pacifists are kind of a waste of space. They don't do anything. I understand his thought, but I think Lewis is confusing secular pacifism with Christian pacifism. Secular pacifism is a pacifism born of humanism. Secular pacifism has this notion that I want to see other humans thrive. This life is all we have, so I don't want to hurt anyone or take their lives. Humans are, at their core, good, and anyone can be changed through training and stimuli. That bad person isn't really evil, but misguided. On secular pacifism, there may be an onus not to harm another human, but the positive ethic of Christ (love, forgiveness, generosity, self-sacrifice, etc) is missing. Often times secular pacifists thrive in a liberal society (as Lewis points out). They live in societies that are wealthy, free, and where it's easy to be an ideological or armchair pacifist.
But this is a mischaracterization if applied to Christian pacifism. True Christian pacifism isn't inaction against evil. Not at all. Pacifism is merely choosing to use means of love to combat actions of evil rather than choosing to fight evil with evil means. One might find this inefficient. Maybe choosing love seems as though it has no effect on evil. But you can't call it inaction. In fact, if you look at the story of pacifists throughout history and their bearing of suffering for the sake of their enemies, then pacifism requires much more difficult actions over longer periods of time than simply choosing to immediately end an evildoer's life in an instant.
War has been universally accepted by governments throughout the ages. Have all governments been wrong? Even if they are wrong, we owe the government our service.
It strikes me that until about 200 years ago, Lewis's argument for perpetuating war would have worked as an argument for perpetuating slavery. Almost all governments had condoned slavery and made laws for it. Since I believe that all humans are born in sin, since governments are just powerful conglomerations of sinners, and since most governments throughout history have failed to have a Christian influence, then yes, I do think it's quite possible for all governments throughout the course of history to be wrong. They were wrong about slavery.
When you look at the early church and the teachings we find on governments and violence, I think Lewis's ideas are easily overturned. Many in the early church seemed to think that all governments throughout history were wrong and that Christ had called them to a higher way. (SEE CHURCH HISTORY). And while the early church did submit, submission is different than obedience. To submit to a government is to submit to their authority, not to obey their every command. This is why Christians could disobey laws on emperor worship, yet submit to the government's authority in receiving punishment for their disobedience. I do not owe the government the service of killing others for them, even if they command it of me.
Almost all of the great minds throughout the ages have declared war necessary and pacifism bad.
This is another appeal to authority or an appeal to consensus from Lewis. I don't blame Lewis for using such an appeal, as I think authority and consensus can be valuable if it is used to bolster other strong, core arguments. But to address Lewis's appeal, most great minds have not been pacifists. But there have been some brilliant and moral people who were. But even if there were none in our history who were pacifists, what would this prove? Individuals are sinful, self-interested, and pragmatic. Of course most people throughout history would be bent towards thinking violence was appropriate at times. Lewis's argument here seems akin to his argument from government consensus, but with less basis due to the numerous brilliant individuals who have been pacifists.
Pacifism rests on ambiguous statements of Jesus and doesn't take all the words of Christ literally.
Should we really give to everyone who asks. Here Lewis attacks the statements of Jesus as being taken too far. This is a completely understandable accusation, as Jesus often used hyperbole and metaphor. However, I have already shown how the cumulative case of other scriptures, testimonies of lives from the Bible, early church tradition and teaching, martyrs for the faith, and implementers of non-violence all help to validate pacifism as not only a valid route, but the route of Christ.
However, I think Lewis spins this argument a different way that is far more convicting to me. Lewis asks why, if we take Christ's words literally here, don't we take him literally when he says in the passage "give to the one who asks of you and do not turn away from the one who wants to borrow from you."? But if Lewis is correct that some pacifists are hypocrites, taking Christ's words on non-violence seriously but not his words on generosity, all he's proven is inconsistency. He may not have proven Christ's words easier than they are and pacifism wrong. He may rather have proved that Christ's words are even harder than bare pacifism, and our love needs to extend even into the generosity and free giving of our wealth. I'm much more inclined to believe the latter, especially as this falls in the same area as the extremely hard teachings that hate is murder and lust adultery. We're not talking about easy things here, we're talking about how even the smallest of things looms large over us.
Pacifism is just self-interest. It gets you out of sacrifice.
Lewis lived during an era where conscription was common. There were two World Wars in a short period of time, and WWII was one of the clearest good vs. evil wars in history - if only in retrospect. When Lewis spoke, then, it seemed to him that pacifism was all too convenient a position to hold, as conscientious objectors could elude conscription and service to their country. They could avoid sacrifice.
I think there are two main problems with Lewis's argument here. The first problem is that, as I've already shown, pacifism often requires more sacrifice and discipline than warring. To take up arms against someone who is attacking me may be hard, but how much harder is it to love them, endure their assault, forgive them, and seek their good? A true pacifist doesn't escape evil just because he or she refuses to do violence. The sacrifice of a pacifist is training their mind and soul to do what few can do - to endure evil head on in love. Their contribution, as some of the early church fathers confirm, was their example to their countrymen and their world. They show by their sacrifice that there is another way to live. There is another, better Kingdom - and it is for everyone, friend or foe. War may seek to bring unity through violence and destruction, but the pacifists know that true reconciliation and a confirmation of the gospel of Christ comes through self-sacrifice. Patriots, like Lewis, seem to say in statements like these that the only true sacrifice worth anything is a sacrifice of body. A pacifist would sacrifice that. But a pacifist is also willing to sacrifice their heart - bearing the the full weight of evil their enemy directs towards them, through love and forgiveness. A soldier may die bodily for his kingdom, but a pacifist is willing to bear not only the weight of death upon the body, but upon their very being, for the sake of the Kingdom.