The title of this article is a contradiction in terms for Richard Dawkins. 'Faith', he tells us, 'requires no justification and brooks no argument.'[1] Its adherents are no more than 'dyed-in-the-wool faith-heads'[2] who have no evidence base to support their beliefs and ignore all evidence against them.

Dawkins' view of faith has an element of truth. In talking with young people about science and religion, I often come across the view that science is about facts and proof and that religion is about opinion and faith. But on further discussion, it is apparent that a better term than 'faith' would be 'credulity' (defined as a 'disposition to believe on insufficient evidence' by Chambers' Twentieth Century Dictionary).

The question that we all face at some time, whether from family, friends or colleagues, is 'so, why are you a Christian?' And most of us dread it. What can we say that will be convincing?

In this article, I would like to consider what different answers we might give and how convincing they may be to a non-Christian. Taking evidence based medicine (EBM) as our guide, we will begin by formulating the question we need to ask. We will then consider some of the different sources and types of response that we might find, and how convincing they are as evidence for the truth of the core beliefs of Christianity. In the process, we will construct a hierarchy of evidence for faith.

Formulating the question

When people ask why we are Christian, the question can be answered on at least two levels. Firstly, we can tell the story of how we became a Christian. The 'testimony' of our journey to faith can be powerful and compelling. But sometimes our friend's questions are more complex. They may really be asking questions such as:

• Does Christianity really make a difference to your life?
• How do you know Christianity is true?

If this is the case, we need to move to a second level of response in which we marshal our arguments that provide evidence for the importance and impact of our beliefs as well as for their truth or validity. Can we offer the sceptic appropriate evidence to show that Christianity can provide meaning and fulfilment in their life? And if so, can we also offer good evidence that our core beliefs as Christians are actually true? One of these without the other is insufficient.

The hierarchy of evidence

The traditional hierarchy of evidence places 'case reports' at the lowest level, with 'systematic reviews' at the highest level. Sometimes only lower levels of evidence are available – or people are happy to consider them initially rather than higher level evidence. But case reports of a drug interaction, for example, will ideally ultimately give rise to further trials that provide better evidence. Similarly, different types of evidence can help to deepen a person's faith and it can also lead them to consider other evidence that can result in a fuller understanding of their beliefs.

I will offer a hierarchy of evidence for Christianity, with the prayer that it may help you to present the type of evidence appropriate to the needs of the non-Christian. Are they looking for evidence on importance or validity? What type of evidence is likely to help them most in their journey to faith? As with EBM, the ideal is to appeal directly to the highest level of evidence that is relevant to the question being asked. The hierarchy is not intended to be a ladder to be climbed. But thinking clearly about the different types of evidence available may help to clarify the evidence that may help someone to move towards a commitment to Christ as Lord and Saviour.

Just because certain evidence lies low down the hierarchy does not mean that it should be ignored as ineffective or irrelevant. It simply means that on its own it does not necessarily decide the key questions about Christianity – there may be other viable explanations of the evidence – and so ultimately higher levels of evidence will be required. Case reports are the lowest level of medical evidence, and yet have resulted in significant findings and consequences (such as the harmful effects of thalidomide when given to pregnant women).

Evidence for belief in Christianity may be split into five main types. We will start with the lowest level of evidence.[3]

Level 5: the nature of the universe

Natural theology is the use of our senses and reason to examine the world in which we live to determine whether or not God exists. It is available to everyone, hence it is also referred to as 'general revelation'. A key biblical text is Romans 1:19,20, which is referring to those who suppress the truth:

…what may be known about God is plain to them… For since the creation of the world God's invisible qualities – his eternal power and divine nature – have been clearly seen, being understood from what has been made…

Creation reveals to us God's eternal and divine attributes. This is echoed in Psalm 19:1: 'The heavens declare the glory of God; the skies proclaim the work of his hands.'

Many scientists look at various aspects of the universe and they conclude that there must be an intelligence, a designer, behind it all. The evidence of the 'fine tuning' of the physical constants that need only change by one part in billions and the world would not be able to support life; the very existence of the universe rather than an eternal nothingness; the emergence of life itself – all these offer evidence for belief in God. Contemporary scientists such as John Polkinghorne, David Wilkinson and Francis Collins see these aspects of the universe as evidence of a designer.

Richard Dawkins' writes in The God Delusion: '…a universe with a creative superintendent would be a very different kind of universe from one without. Why is that not a scientific matter?'[4] Here we can agree with Dawkins. The existence or non-existence of a creator God surely must make a difference to the nature of the universe in which we find ourselves.[5] The universe bears the imprint of its designer.

Even non-religious scientists find that the universe suggests to them a purpose or an intelligence behind it. As just one example, physicist Paul Davies concludes his book The Mind of God, with the words 'We are truly meant to be here.'[6]

So why do I place this at the lowest level of evidence? The reason is that the God it points to is not necessarily the God of Christianity. This is a powerful, intelligent, creative and perhaps purposeful God. But the design of the universe does not necessarily indicate that its designer is loving, or that he cares about his creation. Nor does this evidence distinguish between the truth of Judaism, Christianity or Islam, for example, all of which claim that God created the universe. The God I believe in is far more than just the creator and designer of the world – he is interested in every individual, and no amount of reasoning can move from a mere designer of the world to someone you can have a real relationship with.

Level 4: the moral universe

If the nature of the universe can only get us so far in understanding what God is like, what else can inform us about God's character? The remarkable thing about human beings is that we have access not only to the external universe through our senses, but also to our own internal thoughts and feelings. One part of that is the almost universal sense that there are certain things that are absolutely right or wrong. It is not just a matter of specific actions being forbidden by society to help it work together productively, but the fact that society forbids it because of the universal realisation that these things are wrong.

In his letter to the Romans, Paul remarks that although the Israelites had the Law given to them through Moses, even Gentiles '…show that the requirements of the law are written on their hearts, their consciences also bearing witness...'[7]

CS Lewis calls this the 'law of nature' or the 'law of right and wrong'.[8] Philosopher GE Moore argued that the sense of right and wrong cannot arise from mere facts about the world. If right and wrong really do have an objective meaning, then that meaning must come from a realm outside the physical world.[9]

Our moral sense shows that the powerful, creative, intelligence that produced the world has absolute moral standards of right and wrong, showing a personal aspect to this being that is reflected in each human being – what the Bible calls 'the image of God.'[10] Morality shows that God is not only intelligent and purposeful, but it suggests also that he cares about our conduct. Most people ultimately acknowledge moral values, especially when they reap the consequences of someone else breaking them through deception or theft or violence. The values that we recognise demand that people are fair and loving in their relationships. And this is no more than a reflection of the nature of the God who imparts to us that recognition of these moral values.

This recognition of a moral God again fails to distinguish Christianity from Judaism and Islam. To do that, we need to look for further types of evidence.

Level 3: religious experience

This is an inner awareness of God's presence and character producing an inner certainty of his existence and love. A personal experience of God's presence through his Holy Spirit and an ever-deepening personal relationship with him is one of the distinctive elements of the Christian faith.

Matthew Wolpert, son of the well-known atheist and biologist Professor Lewis Wolpert, says that 'through some very clear, definite experiences, I started to believe in God.'[11] God can and does change our lives, and he transforms our emotions and desires.[12] But it seems to me that inner experience is not primary evidence – it follows on from, but should not replace, other evidence. Certainly, our experience of God is helpful and real for us, but it is not very useful for convincing other people that God is real.

Many people claim to receive religious experiences and we surrender all rights to the claim that Christianity is true if we base our belief on a religious experience alone. Muhammad's experience of receiving the Qur'an from the angel Gabriel presumably seemed real to him, but that does not make it true. Some Muslims claim to know God through their inner experience of him and they describe this in a way that is barely distinguishable from the descriptions of Christians. Feelings and emotions are not a good guide to truth.

If Christianity is true, then we can confidently expect God to respond to those who earnestly seek him, transforming lives into the likeness of Christ.[13] We recognise that it is the Spirit of God working in us, because we have other evidence that convinces us that Christianity is true and because Jesus promised us his Spirit.[14] We know our experience to be true because we understand, on separate evidence, that the one in whom we trust is himself trustworthy.

Scriptural evidence

The top two levels of evidence are based on reliable documents that describe God's action in the world – Scripture. A vital part of our ability to provide evidence for our Christian beliefs is being able to show why Scripture is reliable and important. We do not need to prove that Scripture is infallible or inspired, but we need to be able to give good reasons for trusting it as an historical document that is important, relevant and therefore worth reading.[15]

Copying process

There is not space here to do more than sketch the evidence for the trustworthiness of the Bible. When the Bible was written, all documents were handwritten on papyrus or parchment, which were liable to deterioration. The New Testament documents were used by the early church for teaching[16] and so it is hardly surprising that the originals no longer exist. Fortunately, and unsurprisingly, many copies were made. This gives us over 5,000 Greek New Testament manuscripts and thousands in other languages. Excerpts of the New Testament are also found in hundreds of thousands of quotations by early church leaders.

Although there were inevitably some errors in the copying process, these are less critical than is sometimes suggested, with the majority being simple spelling errors and none making critical differences to any key belief of Christianity.[17] In comparison with other first century historical documents, the New Testament documents deserve far more confidence, both for the relatively minor interval between the original documents and the earliest copy available to us, and for the number of copies available.

For example, historians only have about ten copies of Caesar's Gallic War, which was composed about 50 BC. The earliest of these copies dates from about 900 years after the book was written, yet no historian seriously doubts the basic accuracy of the history recorded there. By comparison, the thousands of copies of the New Testament, with the earliest fragment dating from probably as few as 40 years after it was first written, gives us high confidence in the fidelity of the text.

The transmission of the text of the Old Testament is more complex. But with the discovery of the Dead Sea Scrolls in 1947, the text of the book of Isaiah as it then stood was checked against a version produced some 1,000 years earlier. This showed remarkably few differences, giving great confidence in the purity of the copying process for the Old Testament documents.[18]

Historical accuracy

Time and again, historical details of biblical texts have been confirmed. The five porticoes of the Pool of Bethesda (Jn 5:2) have been excavated.[19] The accuracy of the many details in the book of Acts (place names, people's names and titles) convinced the once sceptical British archaeologist Sir William Ramsay to take the claims of the New Testament seriously, and he became a Christian as a result.[20]

The Times newspaper recently reported [21] that the name of Nebo-Sarsekim, an official mentioned in Jeremiah 39:3 as being present at the siege of Jerusalem, had been found on a cuneiform tablet translated by the British Museum. The Times called this 'dramatic proof of the accuracy of the Old Testament'. The list of similar items could go on, illustrating the key point: both Old and New Testaments need to be taken seriously as accurate historical records of the events they describe.

Level 2: fulfilment of prophecy

If you read Matthew's Gospel you will find that his theme can be summed up in one word – fulfilment. Jesus fulfilled the Old Testament prophecies about him – from his virgin birth to his death and resurrection. He fulfilled the role that the Old Testament animal sacrifices had pointed to, offering salvation and the restoration of each individual's relationship with God.

Unfortunately, prophecy has been given a bad name by groups who predicted future events that did not come to pass. The sceptic is provided with further ammunition when different interpreters claim different meanings for the same scriptural prophecy. There is a common opinion that vague writing can be (mis)interpreted according to the preconceptions of the interpreter and so all such interpretations can be rejected.

Nevertheless, the misuse of something does not invalidate its correct use. There is not space here to delve into any specifics, but the arguments are summarised in lots of different books – two key ones are Evidence that Demands a Verdict [22] and Evidence for Faith.[23]

If God exists, we should expect his utterances about the future to be utterly reliable. Christianity claims that they are. Particularly in the life of Jesus Christ, we can see those prophecies brought to a wonderful fulfilment as God himself enters the world as a human being. If some prophecies have been fulfilled in the past, then it is reasonable to suppose that we can trust the rest to be fulfilled in the future. It is often easier to see the fulfilment in hindsight rather than in foresight, but the fulfilment is then very clear. So we must not be too prescriptive and claim knowledge that we do not have.

Level 1: God's involvement in the world

We finally come to the evidence that is at the top of my hierarchy – God's direct involvement in the world, specifically through miracles and supremely through the resurrection of Jesus. There are lots of claims that miracles happen and the Gospels record a number of Jesus' miracles. Scientists often dispute the very possibility of miracles and this is one of the reasons that the Bible is often dismissed as being nothing but made-up stories and myths.

But if God exists and if he created the universe, then it is quite reasonable to assume that he can act in that universe as he sees fit. At the very least, it is totally unscientific to dismiss the very possibility of a particular phenomenon or event on the grounds that 'such things do not happen'.[24]

Once we acknowledge the Creator, who made this universe with all of its 'laws of nature', we are in no position to state how he might or might not choose to act in his own creation.

The miracle that is at the heart of the Christian faith – the resurrection of Jesus Christ – is probably also the best documented. The evidence is in the form of a number of independent historical eyewitness accounts (Matthew, John, 1 Corinthians), an account by one who spoke to eyewitnesses (Mark's gospel based on Peter's testimony), and an account by a careful historian who had studied many other written accounts and who had spoken to many of the eyewitnesses (Luke).

The evidence is clearly not concocted, for no-one would invent the fact that women, whose testimony was barely valued, were the first witnesses. Nor would anyone be prepared to die for a cock-and-bull story that they knew to be untrue.[25] Peter, one of Jesus' closest disciples, wrote: 'We did not follow cleverly invented stories when we told you about the power and coming of our Lord Jesus Christ, but were eyewitnesses of his majesty.'[26]

If, without prior assumptions, a person uses the same standards of proof and evidence in looking at the Gospel accounts as they do in everyday life, the resurrection stands as clear evidence that Jesus was who he said he was and that his teaching can be believed. Once a person realises that Jesus rose from the dead, God is no longer a theoretical hypothesis; the content of Jesus' teaching can no longer be ignored, but it demands a response of commitment and worship. That is why miracle is at the top of the hierarchy of evidence.

Conclusion

The hierarchy of evidence for our faith can help us to appreciate the diversity and strength of that evidence. It is strong and effective, especially in combination. As we consider the evidence, our own faith will be built up. We do not need to pick and choose which pieces of evidence we consider.

It is all available to be pondered and to strengthen our own faith. We can offer this evidence as appropriate to those who are interested, to present Christ crucified.

Ultimately the Holy Spirit works in people as he wills. We can only try to work with him to play our part in helping others to consider the evidence that leads to a solid faith and trust in Jesus Christ as Lord and Saviour.