I recently spent the evening with a man who lost £750,000 through online betting. It started with a free bet on a rugby match but pretty soon he was hooked. He lost his home, his life saving and his family in the process.

His tragic story confirmed my general anti-gambling stance. I have never bought a lottery ticket or bet on a football match, and rarely even buy a raffle ticket. But the 17^th century intellectual Blaise Pascal argues that a wager might just save a soul, especially if that wager is on God.

Born in 1623 in France, Pascal was a child prodigy and he went on make huge contributions in mathematics, physics and philosophy. He held a correspondence with the mathematician Pierre de Fermat on how to solve the mathematical problems around gambling. One of Pascal's friends wanted to work out when the best time to bet on a game of dice was and wrote to Fermat about it. They worked on the numbers together and ended up laying the foundations of probability theory.

This seems to have prompted another train of thought in Pascal's mind. In a collection of papers, articles and sometimes just fragments of arguments and notes found after his death and published as his Pensées, one of his most significant contributions to Christian thought was discovered. This idea has become known as Pascal's Wager: "Let us weigh the gain and the loss in wagering that God is. Let us estimate these two chances. If you gain, you gain all; if you lose, you lose nothing."

Let me put it another way. Imagine you are drowning at sea. Certain death awaits you. But then you see a lifeboat floating towards you. A voice tells you that it may well be rigged to explode if you climb on board. There is no way to know whether this is true or not. What should you do? The logic of Pascal's wager is that you might as well swim to the boat. If you do not, you will die anyway so you lose nothing except the effort taken to get to the boat. If you get to the boat and it has no bomb then you have survived, which is an infinitely valuable outcome to you.

Does the argument behind Pascal's wager hold water? Both Christians and atheists have questioned its morality and its veracity. It is not often spoken about or used in popular apologetics. But a new book by US theologian Mark Rota is seeking to revitalise the argument. As I read the book I considered how helpful Pascal's logic may be for people I know.

Let's imagine a young woman called Jane. She has a well-paying job in the city. She is good with numbers and she has reached a point in her life where she realises that she has never really examined the veracity of Christianity. She has always assumed that it was fictitious. But intrigued by the positive impact that the Christian faith has had on one of her friends and the attractiveness of Christian moral teaching around caring for the vulnerable, she decides to take a closer look at the Christian faith. As she examines the evidence for Christianity she realises she needs to make a decision. But she does not have irrefutable proof of Christianity and she realises that it is not always easy to claim to be a Christian. She sketches out the pros and cons on the back of an envelope and then summarises her choice like this:

As Jane contemplates these choices, it seems obvious that the only option worth staking anything on is the first because the potential winnings in this life and the next far outweigh any stake involved. She would not want to miss out on the possibility of hope, meaning, purpose, relationship with God and eternal life. According to the logic of the wager, if Jane becomes a Christian and it turns out to be false as there is no God, then there has been some cost incurred but it is insignificant compared to what could have been gained. But if Jane doesn't become a Christian and it turns out to be true, then according to Christianity's own narrative she is in serious trouble with judgment and punishment awaiting her. If Jane doesn't commit to God and atheism is true than she is proved correct, she has lived her life as she pleased which brings benefits, but as life is short these benefits are finite.

Over the centuries there have been many objections to Pascal's argument and in Rota's book many of them are helpfully challenged.

How can you talk about betting on God? Isn't gambling immoral?

The idea of betting seems to be intrinsically problematic to some Christians. With addictive gambling at such epidemic levels it is easy to understand why. So using the metaphor of a bet as the controlling metaphor for the decision to become a Christian could be unhelpful.

However the Bible does not seem to be worried about negative implications of using metaphors. Just because a metaphor is used a certain way doesn't mean the Bible endorses every way that metaphor could be utilized. God wagers with Satan over the response of Job to suffering. Because the book of Job uses gambling as a rhetorical device doesn't mean that there is divine support for online casinos or the national lottery.

Rota also reflects that at the heart of the parable of the Prodigal Son story is one young man working through a decision making process that looks a little like Pascal's wager. At the end of his resources, feeding pigs and hungry enough to eat their swill, the prodigal reasons to himself that he would be better off going back to his father and asking for employment as a servant. He has nothing to lose by asking, and the potential gain of regular meals. This is hardly the most noble of motives. But his calculated decision pays off – he gets much more than food on his plate.

Although the language may be difficult for those of us inclined to avoid bets of any sort, the logical decision-making process at the heart is something that has biblical warrant.

Is the wager intellectually dishonest?

What if you can't bring yourself to believe in God? How can you force yourself to believe what you don't? How can you swim towards a lifeboat you don't believe is even there in the first place? Well-known atheist activist Sam Harris argues "The greatest problem with the wager – and it is a problem that infects religious thinking generally – is its suggestion that a rational person can knowingly will himself to believe a proposition for which he has no evidence."

Harris' challenge to Pascal's wager shows a lack of understanding when it comes to the question of faith. The Bible does not ask anyone to take a blind punt on the truthfulness of the Christian faith. It presents the faith as a response to the evidence. For example Jesus asks his followers to "believe on the evidence of the miracles themselves" John 14.11. In the evangelistic presentations in Acts evidence for the credibility of Christianity is provided by Jesus' fulfilment of Old Testament prophecies or the historical event of the resurrection. Faith is not a blind leap but an informed step responding to the evidence.

Pascal's wager makes best sense when used as a closing argument in the case for Christianity. When other evidences and lines of reasoning have been employed Pascal's wager is a helpful way to evaluate the significance of the decision and the outcomes that are possible.

What about the cost of discipleship?

One of the ongoing objections I had with the way that Pascal's wager was framed was Paul's question in 1 Corinthians 15:19 where he writes: "If only for this life we have hope in Christ, we are to be pitied more than all others." In other words, Paul believes that Christianity is so costly that it is not worth doing if at the end of it all there is no life beyond the grave. He recognises that living in a counter-cultural way will lead to scorn, hatred and persecution. 

Rota argues that whatever suffering we endure for the sake of Christ, it is still finite in quality and quantity and is nothing compared with the treasure that the gospel offers. This idea seems to echo what Paul argues in 2 Corinthians 4:12 when he writes, "For our light and momentary troubles are achieving for us an eternal glory that far outweighs them all." Paul has the right to write those words as he has suffered physically, emotionally, socially and financially for the sake of the gospel. Living for Christ will eventually cost him his life, yet Paul can see the infinite worth of eternity with God in the coming Kingdom. So even when the cost of discipleship is factored in, as it must be, still the logic of the wager holds true.

What about other religions?

The existence of other religions definitely complicates the decision matrix. To revisit our drowning man illustration, it is the equivalent of there being other lifeboats for us to swim towards. Rota argues that it does not render the wager redundant as opting for a faith that promises eternal life offers a significant benefit over atheism which offers only mortality. To swim for any of the lifeboats gives you a better chance that sure death by drowning. But Rota helpfully points out there is lots of good evidence for picking Christianity over the other faiths even in terms of cost-benefit analysis and so it is more than just a random punt on one religion over the others.

So what do you think – should you bet on God?

Imagine a young woman deciding whether she would like to marry her boyfriend. She may be uncertain whether to marry him or not and so may construct a list of his positive attributes and the benefits that life with him would entail. She might even put a relative score against the positives and the negatives. Some might dismiss the young woman as calculating while others would see her as prudent. If it helps her to make an informed decision it is useful. But I wouldn't say that this is a necessary step that all couples thinking about marriage should go through.

In the same way I don't think Pascal's wager is a magic bullet that will help everyone to come to faith. I don't think such a presentation of the gospel exists. There are many different ways of presenting the gospel in the Bible and so I am nervous about any course, sermon or resource or strategy that claims to be the single solution for the salvation of humanity.

The recovery of Pascal's Wager as a means of presenting the critical choice in front of all of us is useful. I think we need to add it to the set of tools that we use to help people explore faith and truly count the cost. If I were a betting man, I'd bet it could help the Church today.

Dr Krish Kandiah @krishk is the founding director of Home for Good and also the executive producer of Books for Life. Visit www.booksforlife.uk for more reading inspiration.

For further reading:

Michael Rota, Taking Pascal's Wager: Faith, Evidence and the Abundant Life, IVP USA
Francis Spufford, Unapologetic, Faber
Tim Keller, Making Sense of God, Hodder