What to say when someone asks for proof of God's existence

It seems so reasonable. It's what any sensible person would ask. Where is the evidence? Why should it be so difficult to believe in Christ?
Hard core atheism, the belief that there is no God (anti-theism), is difficult to defend, so the new softer, friendlier atheism defines itself as "we would believe in God if there was enough evidence". Most of the atheists you will meet are in reality agnostics (no-knowledge). It seems reasonable and humble to admit that we do not know. This softer position says I do not know because there is not sufficient information. I can't prove there is no God and you can't prove there is. Provide me with the
information and of course I would believe. This position is best summed up by Bertrand Russell's statement that if he met God and was asked why he did not believe he would declare, "Because you did not provide enough evidence".
Perhaps apathy is the predominant thought here. Many of your friends do not lie on their beds at night pondering the meaning of life and suffering from existential angst. They are far more concerned about the game they just watched, the bills they have to pay, and their next visit to the doctor. Normal life for them does not involve God.
So just as in the film Jerry Maguire, when Cuba Gooding Jnr asks Tom Cruise to "show me the money", so our atheist/agnostic friends make this seemingly innocuous demand: "show me the evidence". Even today I came across an atheist writer in a local newspaper, proudly asserting that we should not have Christian schools because we should only teach children facts based on evidence and Christianity is not based upon evidence. So how do we respond to this? Let's talk about pride and prejudice.
Pride. Behind this seemingly humble and reasonable request there is actually a vast amount of pride. The trouble is that the person making this claim assumes they are in the position of being able to judge the evidence. They assume they have the neutrality, intelligence and ability to assess whether there is a God or not. They have, in effect, positioned themselves as the judge of The Judge. "I will not believe in a God who does X, Y or Z", is a common claim. So the first question I simply ask anyone who demands evidence, is why they think they have the capacity to judge any such evidence? You cannot see God without humility. It is only when we kneel at the cross, rather than flying over it at drone height, that we are able to see where love and mercy meet. That is why Bertrand Russell will not be standing on the Day of Judgement accusing God; he will be kneeling at the name of Jesus, astounded and ashamed that he was so blind.
Prejudice. Very often, the person who demands evidence has already made a pre-judgement that there can be no such evidence. It's a bit like arguing with a conspiracy theorist. No matter what you say, it is automatically dismissed, because it is perceived as being part of the conspiracy! I have often found that if you answer a particular problem, or provide a particular piece of evidence, the person you are answering immediately turns to something else and just avoids the issue. In order to overcome this prejudice and to avoid wasting a vast amount of time arguing about such vital issues as whether Noah walked to Australia to get kangaroos, I would simply suggest the following: ask anyone who demands evidence, what evidence is it that they would accept for God? Honest atheists like Richard Dawkins admit that there is almost nothing that would convince them of God. If a giant finger was to write in the sky, "I exist", they would find some alternative way of explaining it. Anything other than believing in an almighty personal Creator.
When the Big Bang was proven and it became clear that the universe did indeed have a beginning, as the Bible stated, some atheists were so desperate to avoid the obvious implications that they refused at first to accept it (and afterwards quickly ran off to place their faith in the unproven multiverse theory). Their philosophy is what I call ABGism (Anything But God). It is not so much that they believe there is no evidence for God, but they are emotionally driven by their desire that there should be no evidence for God.
I was blind but now I see. In reality the situation is even worse than that. When you ask people to believe and trust in God, it is like asking a blind person to admire the intricacies of the Mona Lisa. You are talking to dead stones and asking these stones to dance. You are calling out to those who are dead in sins and trespasses, to come to life. It's enough to make any self-respecting evangelist, preacher, Christian give up in despair. Except for those who know their God and his Bible! Because the Bible itself tells us that the word of God will not return to him empty, and that the Holy Spirit takes the word and enables the blind to see and the dead to live. The word preached and lived in the Dunamis (power) of the Spirit is dynamite!
Does this mean that there is no room for evidence? Of course not! The Holy Spirit always uses means. He usually addresses the heart through the mind, not the other way round. Therefore we should patiently present all the evidence that he gives us with the prayerful desire that he will take this and work in the lives of those we deal with. For most people, coming to faith in Christ is not a Damascus road experience. It is not one gigantic leap up Mount Improbable, but rather an evolving faith over a period of time, with the Holy Spirit using a number of factors, including evidence, experience, the Bible, coincidence, friends, foes and family.
I often tell people that they should use the motto of The X-Files – 'the truth is out there'. An intelligent agnostic is someone who seeks that truth. A loving Christian is someone who seeks to present that truth. At the end of The Dawkins Letters I presented my 10 different reasons for believing that Christianity is true. The creation, the human mind and spirit, the moral law, beauty, religion, experience, history, the church, the Bible, and Jesus. Why not make your own list?
In today's Christian world we are blessed with a significant number of books that intelligently, attractively and insightfully present the evidence for Jesus Christ. My recommended book this week is Josh McDowell's New Evidence that Demands a Verdict. It's lengthy, but it contains a wealth of information.
Christians who seek to present the good news of Jesus Christ will be prayerful, loving people who are saturated with the word of God and who know how to present it in the context of a culture which is deaf, dumb and blind to that word. If we do so, we will not just be presenting the evidence, we will be the evidence.