Faith, Proof and Evidence: What’s right to think?

24 November 2015

Faith, Proof and Evidence:
What's right to think?

Professor Alister McGrath

The whole issue of making sense of reality is deeply embedded within both the natural sciences and the Christian faith. In my own case, one factor that led me decisively away from my youthful atheism to Christianity was my growing realization that the Christian faith made far more sense of what I saw around me and experienced within me than its atheist alternatives. I gladly endorse C. S. Lewis's statement, now inscribed on his memorial stone in Poet's Corner, Westminster Abbey: 'I believe in Christianity as I believe that the Sun has risen, not only because I see it, but because by it I see everything else.

Yet there is more to Christianity than making sense of things. We can hardly overlook its emphasis on the existentially transformative nature of salvation, nor the rich experience of beauty and awe which is so often evoked in Christian worship. Yet the fact remains the intellectual capaciousness of faith cannot be overlooked. As the Harvard psychologist William James suggested many years ago, religious faith is basically 'faith in the existence of an unseen order of some kind in which the riddles of the natural order may be found and explained.

I concede that this aspect of Christianity can be overemphasised, leading to an impoverishment of faith. Dorothy L. Sayers, unquestionably one of the finest lay theologians of the twentieth century, was convinced that Christianity seemed to offer 'the only explanation of the universe that is intellectually satisfactory.' Yet she subsequently wrote to William Temple, then archbishop of Canterbury, confessing that was so attracted to this aspect of Christianity that at times she wondered whether she had 'fallen in love with an intellectual pattern.' Looking back on my own exploration of my faith, I can see this failing – and it is a failing! – reflected in my own early thinking. Yet as I grew in faith, its imaginative and aesthetic dimensions became increasingly evident to my mind, and increasingly important to my theological articulation. Yet that intellectual foundation remains firmly embedded in my mind, giving structure and stability to everything else that is based upon it.

At the other end of this spectrum of possibilities, we might note the brilliantly argued critique of the 'New Atheism' provided by Terry Eagleton, who was severely critical of those who treat religion as a fundamentally explanatory phenomenon. 'Christianity was never meant to be an explanation of anything in the first place', he wrote. 'It's rather like saying that thanks to the electric toaster we can forget about Chekhov.' Eagleton suggests that believing that religion is a 'botched attempt to explain the world' about as helpful as 'seeing ballet as a botched attempt to run for a bus.

Now Eagleton is surely right to argue that there is more to Christianity than an attempt to make sense of things. Yet this explanatory theme is – as Dorothy Sayers appreciated – part of its rich heritage. Christians have always held that their faith makes sense in itself, and makes sense of the enigmas and riddles of our experience. The gospel is like an illuminating radiance that lights up the landscape of reality, allowing us to see things as they really are. The French philosopher Simone Weil (1909-43) made this point especially well, and I would like to cite from her in making this point:

If I light an electric torch at night out of doors, I do not judge its power by looking at the bulb, but by seeing how many objects it lights up. The brightness of a source of light is appreciated by the illumination it projects upon non-luminous objects. The value of a religious or, more generally, a spiritual way of life is appreciated by the amount of illumination thrown upon the things of this world.

The ability to illuminate reality is an important measure of the reliability of a theory, and an indicator of its truth. The best theory is thus likely to be the one that is able to fit in observations and experiences most elegantly, most simply, most comprehensively, and most fruitfully.

Let us look at C. S. Lewis as we explore this point further. As many of you will know, Lewis was an atheist as a young man, taking the view that modern science (by which he meant the science of the 1910s) had discredited faith. So what were his reasons for returning to faith after his atheist experimentations? In an unpublished manuscript, dating from around 1930, recording his musings about his conversion, Lewis makes a remarkable statement, which merits close attention. 'I am an empirical theist. I arrived at God by induction.

Lewis may well have found this way of thinking already expressed in the writings of his great hero, G. K. Chesterton. After his initial agnosticism, Chesterton's spiritual journey took a decisive new turn in 1903. He published a newspaper article explaining why he and many others now regarded Christianity with intense intellectual seriousness. 'We have returned to it because it is an intelligible picture of the world.' Chesterton realized that testing a theory meant checking it out against observation. 'The best way to see if a coat fits a man is not to measure both of them, but to try it on.' Let Chesterton himself explain what he has in mind.

Numbers of us have returned to this belief; and we have returned to it, not because of this argument or that argument, but because the theory, when it is adopted, works out everywhere; because the coat, when it is tried on, fits in every crease . . . We put on the theory, like a magic hat, and history becomes translucent like a house of glass.

Chesterton's argument is that it is the Christian vision of reality as a whole – rather than any of its individual components – that proves so compelling. Individual observations of nature do not 'prove' Christianity to be true; rather, Christianity validates itself by its ability to make sense of those observations. Listen to one of Chesteron's statements, which seems to me to be both beautifully phrased and fully of inductive insight: 'The phenomenon does not prove religion, but religion explains the phenomenon.' For Chesterton, a good theory – whether scientific or religious – is to be judged by the amount of illumination it offers, and its capacity to accommodate what we see in the world around us and experience within us. 'With this idea once inside our heads, a million things become transparent as if a lamp were lit behind them.' Once more, we note an implicitly inductive approach being adopted to apologetic questions, fitting in well with the habits of thought of many scientists.

One of the most interesting issues in science and religion concerns the nature of 'proofs' of theories – whether the theory in question is Einstein's theory of relativity, or the Christian affirmation of the existence of God. When I first began to study science as a teenager, back in the 1960s, I was encouraged to think that science proved its findings with total conviction. The chemical composition of water, for example, could be proved to be H2O. It is a commonplace for those committed to the outmoded 'warfare' model of the relation of science and religion to contrast them at this point. Science and religion are often placed at opposite ends of the scale on the question of evidence.

Richard Dawkins is a vigorous advocate of this approach. He argues that science proves things by an appeal to evidence, where religion runs way from the evidence. 'Faith', he tells us, 'means blind trust, in the absence of evidence, even in the teeth of evidence.' Dawkins argues that there is no need for faith in science, in that the evidence for a correct conviction compels us to accept its truth. He first set out his views on this matter in The Selfish Gene in 1976. This passage seems to me to be especially important:

[Faith] is a state of mind that leads people to believe something – it does not matter what – in the total absence of supporting evidence. If there were good supporting evidence, then faith would be superfluous, for the evidence would compel us to believe it anyway.

Though this seems clear, it is actually not a sustainable view of the relation of evidence and belief in the natural sciences, in that it fails to make the critical distinction between the 'total absence of supporting evidence' and the 'absence of totally supporting evidence.' For example, consider the current debate within cosmology over whether the 'big bang' gave rise to a single universe, or a series of universes (the so-called 'multiverse'). I have many distinguished scientific colleagues at Oxford who support the former approach, and equally distinguished scientific colleagues who support the latter. Both are real options for thinking and informed scientists, who make their decisions on the basis of their judgements of how best to interpret the evidence and believe – but cannot prove – that their interpretation is correct. This observation – to which others could easily be added – does not fit at all with Dawkins's bold declaration that 'if there were good supporting evidence, then faith would be superfluous, for the evidence would compel us to believe it anyway'. Dawkins himself clearly believes in the 'multiverse' theory. But the evidence for it just isn't good enough to compel him – or anyone else – to accept it. I gladly accept that it might suggest this approach or that it could be argued to be consistent with it – but it does not compel us to accept it.

In its rigorous sense, the notion of 'proof' applies only to logic and mathematics. We can prove that 2 + 2 = 4, just as we can prove that 'the whole is greater than the part'. In science, as we make a series of observations, we are forced to address the question: what must be true if we are to explain what is observed? What 'big picture' of reality offers the best fit? The American scientist and philosopher Charles S. Peirce (1839-1914) used the term 'abduction' to refer to the way in which scientists generate theories that might offer the best explanation of things. The method is now more often referred to as 'inference to the best explanation'. Let us explore this further.

A classic example of this approach can be found in Charles Darwin's Origin of Species (1859), now widely seen as a landmark in scientific history. Darwin himself believed that his theory of 'natural selection' provided the most elegant and persuasive explanation of biological life forms. But he knew he could not prove it. The problems were clear. To begin with, there was no 'smoking gun' – no knock-down, unambiguous evidence which would conclusively and incontrovertibly compel people to accept his theory. Everything that was known about the natural world could be accommodated by rival theories, such as transformism. Furthermore, there were serious scientific objections and difficulties to his theory, which made many scientists of his day believe it was unacceptable. The most significant of these was probably the problem of genetic dilution. Darwin lacked a working theory of genetics to explain how inherited characteristics were transmitted to subsequent generations.

Yet despite some formidable difficulties, Darwin believed that his theory was right, and would one day be shown to be right. How, he asked, could a theory be wrong when it made so much sense of what he observed? Yes, there were loose ends everywhere, and a large number of problems. But his core idea seemed to him to be correct – despite the fact it could not be proved. He expressed his hope as follows towards the end of The Origin of Species:

A crowd of difficulties will have occurred to the reader. Some of them are so grave that to this day I can never reflect on them without being staggered; but, to the best of my judgment, the greater number are only apparent, and those that are real are not, I think, fatal to my theory.

In the case of the natural sciences, the question is thus how to make sense of an accumulation of observations of the natural world. What 'big picture' makes most sense out of these observations? This usually involves the process of 'inference to the best explanation'. Yet this is always understood to be a provisional assessment – what the noted psychologist William James (1842-1910) called a 'working hypothesis', which was open to revision as evidence amounted and reflection proceeded. Today, on the basis of the evidence available to us, we might accept this scientific theory; tomorrow, on the basis of new evidence or revised interpretations of old evidence, we might accept a quite different scientific theory.

As Michael Polanyi (1891-1976), a chemist and noted philosopher of science pointed out, natural scientists find themselves having to believe some things that they know will later be shown to be wrong – but not being sure which of their present beliefs would turn out to be erroneous. That is why Polanyi's book Personal Knowledge (1958) is so important to reflective scientists. It sparked off a long overdue discussion about the limits of certainty in science, and how scientists ought to respond to this issue. Polanyi (1891-1976) was a Hungarian chemist turned philosopher, who found himself to be increasingly troubled by his need to commit himself to what he believed (scientifically) to be true, while knowing that some of this would later be shown to be false. He argued for the need to speak of science as 'personal knowledge' – not absolutely certain, yet still capable of eliciting justified belief.

In many ways, Polanyi's work illuminates the frail condition of humanity as much as the nature of science. Scientific knowledge is not generated infallibly by a mechanical process, but involves our personal – and fallible – judgement that certain beliefs are reliable, and to be trusted. Polanyi insisted that we must understand that commitment to beliefs – scientific or otherwise – inevitably transcends the evidence underlying them. And every now and then, evidence emerges that something which scientists believed to be true really was true.

Scientific theorizing offers what is believed to be the best account of the experimental observations currently available. Radical theory change takes place either when it is believed that there is a better explanation of what is currently known, or when new information comes to light which forces us to see what is presently known in a new light. Unless we know the future, it is impossible to take an absolute position on the question of whether any given theory is 'right'. We simply do not know which of today's theories will be discarded as interesting failures by future generations. Yet this does not prevent scientists from committing themselves to a given theory, believing that it is right (while knowing it may prove to be inadequate or wrong in the longer term).

This emphasis on the provisionality of scientific theories is not in any way a criticism of the natural sciences. It is simply a recognition of how the scientific method works. Historians of science regularly point to a group of theories which were scientific orthodoxy in their age, and are now regarded as clearly incorrect.

To explore the importance of this point, let us ask a question: is Darwin's theory of evolution right? The best answer to this question would probably be that Darwin's theory, as modified by his successors, is currently believed to be the best explanation of a vast body of biological data. Yet as more and more data builds up, there is a possibility that what Thomas Kuhn calls a 'paradigm shift' may take place. In other words, there may be a radical theory shift away from Darwinism towards some new theory, at present unknown. Richard Dawkins, who as you all know is an enthusiastic advocate of Darwinism, is quite clear about this point:

Darwin may be triumphant at the end of the twentieth century, but we must acknowledge the possibility that new facts may come to light which will force our successors of the twenty-first century to abandon Darwinism or modify it beyond recognition.

So what about religious beliefs, especially those grounded in an interaction with the natural world? The most interesting question here is whether belief in God can be proved, in a way similar to the proof of a scientific theory. Given the topic of this lecture, it seems important to look at these in a little more detail. It is generally agreed that there are three general categories of arguments for the existence of God which are of particular importance in relation to the natural sciences. I am going to look at three today. These are generally referred to as the cosmological, teleological and kalam arguments, although there is some debate about whether the third is to be regarded as a distinct category or argument in its own right, or a category of the more general cosmological argument. For our purposes in this lecture, we shall assume that it requires separate discussion as an argument in its own right.

The Cosmological Argument

During the Middle Ages, Thomas Aquinas (1225-74) set out a suite of reasons for believing in God, often referred to as the 'Five Ways'. One of these is known as the 'argument from motion'. It argues that the observation of change or motion in the world points to the existence of a first cause which is responsible for them. There must be a 'prime unmoved mover' which causes change in the world. This 'first cause' argument is now often referred to as the 'cosmological argument'. As Aquinas states it, the argument takes the following form.

Motion and change are observed within the world.

Everything that moves or changes is changed by something else.

Since there cannot be an infinite series of causes for a given event, the chain of causality must terminate at a first cause.

There can be no doubt that this first cause or 'prime unmoved mover' is none other than God.

In more recent times, this argument has been restated in more explicitly cosmological terms (hence the title now widely used to refer to it). The most commonly encountered statement of the argument runs along the following lines:

Everything within the universe depends on something else for its existence;

What is true of its individual parts is also true of the universe itself;

The universe thus depends on something else for its existence for as long as it has existed or will exist;

The universe thus depends on God for its existence.

The argument basically assumes that the existence of the universe is something that requires explanation. It will be clear that this type of argument relates directly to modern cosmological research, particularly the 'big bang' theory of the origins of the cosmos. This is also true of the kalam version of the cosmological argument, to which we now turn.

The Kalam Argument

The argument which is now generally known as the 'kalam' argument derives its name from an Arabic school of philosophy which flourished in the early Middle Ages. The basic structure of the argument can be set out as four propositions:

Everything which has a beginning must have a cause;

The universe began to exist;

Therefore the beginning of the existence of the universe must have been caused by something;

The only such cause can be God.

Although some scholars regard this as a variant of the cosmological argument, already set out above, others regard it has having distinct features, meriting its treatment in its own right.

The structure of the argument is clear, and its implications need little in the way of further development. If the existence of something can be said to have begun, it follows – so it is argued – that it must have a cause. If this type of argument is linked with the idea of a 'Big Bang' (00-0), its relevance for our discussion will be clear. Modern cosmology strongly suggests that the universe had a beginning. If the universe began to exist at a certain time, it must have had a cause. And what cause could there be other than God?

This form of the kalam argument has been widely debated in recent years. One of its most significant defenders has been the philosopher William Lane Craig (born 1949), who sets out its main features as follows:

Since everything that begins to exist has a cause of its existence, and since the universe began to exist, we conclude, therefore, the universe has a cause of its existence . . . Transcending the entire universe there exists a cause which has brought the universe into being.

Debate over the argument has centred on three questions, one of which is scientific and the other two of which are philosophical.

Can something have a beginning without being caused? In one of his dialogues, the great Scottish empirical philosopher David Hume (1711-76) argued that it is possible to conceive of something that comes into being, without necessarily pointing to some definite cause of that existence. Nevertheless, this suggestion raises considerable difficulties.

Can one actually speak of the universe having a beginning? At one level, this is a profoundly philosophical question. At another, however, it is a scientific question, which can be considered on the basis of known observations concerning the rate of expansion of the universe, and the background radiation evidence for the 'big bang'.

If the universe can be considered to have been 'caused', can this cause be directly identified with God? One line of argument of note here takes the following form. A cause must be prior to the event which it causes. To speak of a cause for the beginning of the existence of the universe is thus to speak of something which existed before the universe. And if this is not God, what is it?

It will be clear that the traditional kalam argument has been given a new lease of life by the 'big bang' theory of the origins of the universe. The philosophical issues which are raised are likely to remain disputed. A similar debate focusses on the question of whether the universe can be said to be 'designed', and we shall consider this issue in what follows.

The Teleological Argument

The 'teleological' argument is often known as the 'argument from design' and is among the most widely discussed of the philosophical arguments for the existence of God. Thomas Aquinas frames the argument in terms of apparent design within the natural order. Things do not simply exist; they appear to have been designed with some form of purpose in mind. The term 'teleological' (meaning 'directed towards a goal') is widely used to indicate this apparently goal-directed aspect of nature. This leads Aquinas to conclude that there exists 'an intelligent being by whom all natural things are directed to their end' – in other words, God.

It is this aspect of nature which has often been discussed in relation to the natural sciences. The orderliness of nature – evident, for example, in the laws of nature – seem to be a sign that nature has been 'designed' for some purpose. This line of approach was developed with particular skill in William Paley's Natural Theology; or Evidences of the Existence and Attributes of the Deity, Collected from the Appearances of Nature (1802). This book had a profound influence on popular English religious thought in the first half of the nineteenth century, and is known to have been read by Charles Darwin. Paley was deeply impressed by Newton's discovery of the regularity of nature, especially in relation to the area usually known as 'celestial mechanics'. It was clear that the entire universe could be thought of as a complex mechanism, operating according to regular and understandable principles.

For Paley, the Newtonian image of the world as a mechanism immediately suggested the metaphor of a clock or watch, raising the question of who constructed the intricate mechanism which was so evidently displayed in the functioning of the world. One of Paley's most significant arguments is that mechanism implies 'contrivance'. Writing against the backdrop of the emerging Industrial Revolution, Paley sought to exploit the apologetic potential of the growing interest in machinery – such as 'watches, telescopes, stocking-mills, and steam engines' – within England's literate classes.

In the early nineteenth century, England was experiencing the Industrial Revolution, in which machinery was coming to play an increasingly important role in industry. Paley argues that it is impossible to take seriously any suggestion that such complex mechanical technology came into being by purposeless chance. Mechanism presupposes contrivance – that is to say, a sense of purpose, and an ability to design and fabricate. Both the human body in particular, and the world in general, could be seen as mechanisms which had been designed and constructed in such a manner as to achieve harmony of both means and ends.

Paley argues that nature bears witness to a series of biological structures which are 'contrived' – that is, constructed with a clear purpose in mind. Paley is at his best when he deals with the description of mechanical systems within nature, such as the immensely complex structure of the human eye, or the heart. So what does this prove? 'Every indication of contrivance, every manifestation of design, which existed in the watch, exists in the works of nature'. Indeed, Paley argues, the difference is that nature shows an even greater degree of contrivance than the watch.

The 'argument from design' was subjected to criticism on a number of grounds by the Scottish philosopher David Hume. The most significant of Hume's main criticisms can be summarized as follows.

The direct extrapolation from the observation of design in the world to a God who created that world is not possible. It is one thing to suggest that the observation of design leads to the inference that there is a design-producing being; it is quite another to insist that this being is none other than God. There is thus a logical weak link in the chain of argument.

To suggest that there is a designer of the universe could lead to an infinite regression. Who designed the designer? We noted that Aquinas explicitly rejected the idea of an infinite regression of causes; however, he fails to offer a rigorous justification of this point, apparently assuming that his readers will regard his rejection of this series as being self-evidently correct. Hume's point is that this is not the case.

The argument from design works by analogy with machines. The argument gains its plausibility by a comparison with something that has clearly been designed and constructed – such as a watch. But is this analogy valid? Why could the universe not be compared to a plant, or some other living organism? Plants are not designed; they just grow. The importance of this point in relation to Paley's argument will be obvious, especially in the light of the Darwinian view that appearances of design arise naturally.

In recent years, new discussions of the rationality of God's existence have begun to emerge, including those based on fine-tuning and anthropic phenomena. A trend of some importance is a move away from deductive approaches to God's existence, towards those based on abduction or inference. Rather than argue that we can deduce the existence of God from causalities within the natural world, many are arguing that God represents the 'best explanation' of the natural world.

There is another point that needs to be made here. The natural sciences are empirical in their approach – in other words, they rely on the application of observation and experiment in investigating the world. Yet empiricism refuses as a matter of principle to speculate about any realities beyond the observable world. Bas van Fraasen, a leading philosopher of science, makes this point clearly.

To be an empiricist is to withhold belief in anything that goes beyond the actual, observable phenomena, and to recognize no objective modality in nature. To develop an empiricist account of science is to depict it as involving a search for truth only about the empirical world, about what is actual and observable . . . it must invoke throughout a resolute rejection of the demand for an explanation of the regularities in the observable course of nature by means of truths concerning a reality beyond what is actual and observable.

This emphasis on what is 'actual and observable' gives the sciences their distinct identity; it also defines their limits.

I am going to end this lecture by looking at an argument for the existence of God that we find in the writings of C. S. Lewis. It's often referred to as the 'argument from desire'. I am going to set it out, and invite you to see what you make of it. It has some problems, and I will make my own concerns clear as we go along. Let us look at a quote which is often taken as a summary of his approach, which comes from his 1952 work Mere Christianity: 'If I find in myself a desire which no experience in this world can satisfy, the most probable explanation is that I was made for another world'. The starting point for Lewis's approach is an experience – a longing for something undefined and possibly undefinable, that is as insatiable as it is elusive. In one sense, of course, this is not an 'argument', in the strict sense of that term. It is better understood as reflection on the best explanation of a resonance of intuitive plausibilities.

Lewis actually sets out versions of an 'argument from desire' at several points in his writings. It is, for example, clearly formulated in the 'Chronicles of Narnia', which often explore a 'longing for Narnia' and a 'longing for Aslan' – two themes which, though clearly inter-related, are nevertheless to be seen as distinct. Lewis sets out versions of this argument at several points in his writings, including the 'Chronicles of Narnia'. The most important statements of the argument, however, are the following:

The Pilgrim's Regress (1933), written shortly after his conversion to Christianity, in which Lewis sets out an allegorical account of his own conversion, focusing on the theme of desire.

The university sermon 'The Weight of Glory', preached in Oxford in June 1941, and subsequently published as an article in the journal Theology. This is the most elegant statement of the argument, which is here framed primarily in terms of the human quest for beauty.

The talk 'Hope', given during the third series of Broadcast Talks for the British Broadcasting Corporation during the Second World War, and subsequently reproduced as a chapter in Mere Christianity. This is generally considered to be Lewis's most influential statement of the argument, and I quoted from this a moment ago.

The autobiographical work Surprised by Joy, in which the theme of 'Joy' plays a significant role in arousing Lewis's openness towards God.

So what sort of experiences of desire or yearning does Lewis have in mind? Let's just look at two examples, taken from very different sources. The great Russian novelist Fyodor Dostoyevsky spoke of 'a nostalgic yearning, bordering at times on unendurably poignant sorrow,' which he experienced in 'the dreams of my heart and in the reveries of my soul.' Bertrand Russell, one of the most articulate and influential British atheist writers of the twentieth century, put a similar thought into words as follows:

The centre of me is always and eternally a terrible pain . . . a searching for something beyond what the world contains, something transfigured and infinite – the beatific vision, God – I do not find it, I do not think it is to be found – but the love of it is my life . . . it is the actual spring of life within me.

Russell's daughter, Katharine Tait, recalled that he was contemptuous of organized religion, dismissing its ideas mainly because he disliked those who held them. Yet Tait took the view that her father's life was really an unacknowledged, perhaps disguised, search for God. 'Somewhere at the back of my father's mind, at the bottom of his heart, in the depths of his soul, there was an empty space that had once been filled by God, and he never found anything else to put in it.' Russell was now haunted by a 'ghost-like feeling of not belonging in this world.'

These are the kinds of experience to which Lewis appeals – a sense of hovering on the brink of discovering something of immense significance, linked with a sense of sorrow and frustration when what seemed to be so close tantalizingly disappears. Like smoke, it cannot be grasped. As Lewis puts it: 'There was something we grasped at, in that first moment of longing, which just fades away in the reality.' So what does this sense of unfulfilled longing mean? To what does it point?

Some people, Lewis concedes, might suggest that this frustration arises from looking for its true object in the wrong places; others that, since further searching will only result in repeated disappointment, there is simply no point trying to find something better than the present world.

Yet Lewis suggests that there is a third approach, which recognizes that these earthly longings are 'only a kind of copy, or echo, or mirage' of our true homeland. Since this overwhelming desire cannot be fulfilled through anything in the present world, this suggests that its ultimate object lies beyond the present world. 'If I find in myself a desire which no experience in this world can satisfy, the most probable explanation is that I was made for another world.

Here, as throughout his apologetic writings, the starting point of Lewis's approach does not lie with the Bible or the Christian tradition, but with shared human experience and observation. How do we make sense of them? Lewis's genius as an apologist lay in his ability to show how a 'viewpoint' which was derived from the Bible and the Christian tradition was able to offer a more satisfactory explanation of common human experience than its rivals – especially the atheism he had once himself espoused.

Lewis's apologetic approach is to identify a common human observation or experience, and then show how it fits in, naturally and plausibly, within a Christian way of looking at things. For Lewis, Christianity provided a 'big picture', an intellectually capacious and imaginatively satisfying way of seeing things. Lewis was always emphatic that nothing can be proved on the basis of observation or experience. Yet while such observations of nature or our own experiences prove nothing, they can suggest certain possibilities, and even intimate what they might mean.

So what are we to make of this approach? I am sure that lots of questions will have occurred to you as I set out his ideas. Here are some concerns that I would express.

The whole approach rests on a subjective experience, rather than an objective assessment of the external world. Does everyone feel like this? Or just some people? And anyway, doesn't this seem to make the argument dependent on my personal feelings and experiences, which cannot be validated externally

The argument actually proves nothing. It affirms the consistency of the ideas, but does not compel assent.

Now much more could be said. But time is not on our side, and I fear that we must leave this conversation here for the present. In our next lecture, we will pick up on some of the themes that I began to touch on when speaking about origination and the "big bang". It is a fascinating topic that needs a lot more attention, and we'll look at this when we next meet.

© Professor Alister McGrath, 2015