The starting-point of Evans' book is the posing of a puzzle: why is it that the traditional arguments for the existence of God are frequently declared to have been conclusively refuted and yet continue to be defended? ‘The arguments never seem to convince the critics’, he says, but ‘the refutations never seem to silence the proponents’ (1–2). Why is this? The question is a good question, and Evans' answer is an interesting and thought-provoking one. The enduring appeal of the traditional arguments is best explained, he suggests, if they are understood not as arguments but as ‘natural signs’ pointing to the existence of a deity. The concept of a ‘natural sign’ is one which he takes from Thomas Reid, but he puts it to a different use from Reid's, and it is the concept at the heart of this book.

What is the difference between arguments and natural signs? Part of the difference, for Evans, is that natural signs are inconclusive. ‘They point to God but they do not do so in a coercive manner’ (2). They are not proofs, and Evans' point sometimes seems to be that the traditional arguments ‘fail to reach the standard of proof’ (132). This would help to explain the stand-off between the defenders and the critics of the traditional theistic arguments. It is not enough, however, to establish that the traditional arguments are not really arguments at all. They might be probabilistic arguments, perhaps having the form of inference to the best explanation, and that could be the reason for their inconclusiveness; it is a matter for judgement, for instance, whether the argument from design or some other hypothesis is the better explanation for the appearance of purposive order in the universe. To distinguish natural signs from arguments, then, Evans needs to say more. His stronger claim is that theistic natural signs are non-inferential. They give us a direct awareness of God's reality, they are ‘a source of basic knowledge’ (154). These seem to be the distinguishing features of natural signs, then: they are direct but inconclusive evidence for God. Evans' thesis is that the traditional theistic arguments should be re-construed as natural signs, and this is his explanation of the initial puzzle. His favoured way of putting it is that the signs can be ‘read’ or ‘interpreted’ in different ways. And that is why no amount of argument can settle the matter.

The central chapters (3–5) of the book take us through three traditional arguments from natural theology: the cosmological argument, the teleological argument, and the moral argument for the existence of God. In each case Evans reminds us of what makes the arguments plausible, reviews the standard objections, and brings out the apparent deadlock. He then suggests that the stand-off can be understood if we recognise that underlying the supposed arguments are certain core human experiences which can be read as forms of direct but inconclusive awareness of God's reality. The cosmological argument builds on our experience of ‘cosmic wonder’, our sense of mystery and our awareness of the contingency of the finite objects in the natural world. The teleological argument is based on our experience of ‘beneficial order’ in the natural world. And underlying the moral argument are two fundamental features of our moral experience: our awareness of the objectively binding character of moral obligations, and our awareness of the intrinsic worth of all human beings. He recognises that all these experiences can be ‘read’ differently by atheists. He recognises also that their ‘information content’ (74) is limited and that they lead at most to a ‘thin theism’ (9). The experience of cosmic wonder points only to ‘some kind of transcendent ground of the natural world’. The experience of beneficial order points to ‘a God who is intelligent and cares about value’. The two aspects of moral experience ‘point to God in a more powerful way’ – ‘to a God who is essentially good, and who desires a relationship with human persons’ (147). The natural signs cannot by themselves, however, furnish a personal relationship with God such as is envisaged in any of the religious traditions. What they provide, Evans suggests, is the first stage of a two-stage theology. They prepare the ground for the ‘special revelation’ which the ‘living religions’ purport to provide and which can give a fuller knowledge of God.

Evans' discussions of the three traditional arguments are clear and balanced, and in each case his introduction of the idea of ‘natural signs’ offers a very interesting and useful way of re-construing the arguments, one which could account both for their enduring appeal and for their inconclusiveness. I won't try to comment in any detail on these three chapters, but I want to pick up one point from what he says about moral experience, which will then lead into some more general questions about the concept of ‘natural signs’.

The two widely-shared aspects of moral experience to which Evans appeals are the experience of objectively binding moral obligations, and the experience of the intrinsic worth of human beings. What I find surprising is that he does not make any significant link between the two kinds of experience. And if one were to do so, then I suggest that his reading of them might look a good deal less persuasive. The experience of binding obligations he interprets in the light of a modified ‘divine command’ theory of the kind proposed by Robert Adams and others. Of the experience of the intrinsic worth of human beings he suggests that ‘it is plausible to interpret such a recognition as a perception of… the “image of God” in humans’ (145). Well yes, that is a possible interpretation of the experience. But why not say what he acknowledges that secular thinkers would say, that this is a core feature of our moral experience simply because ‘humans do have such worth’ (144)? Of course there are plenty of problems here and a lot more would have to be said, but it is no more problematic and a good deal less question-begging than saying that humans have intrinsic worth because they are made in the image of God. And if we were prepared to say that the experience is grounded in what makes human beings human, rather than in any relation to a divinity, then we could also see the experience as grounding our sense of binding moral obligations. As Evans says, the case for a divine command theory rests on a social theory of obligations – that obligations are binding on us in virtue of our relationships to other persons. But in that case a natural explanation of why we experience at least our most fundamental moral obligations as binding on us regardless of our desires is that they are obligations to other human beings and are grounded in our recognition of the intrinsic worth of human beings. In other words, there is readily available an interpretation of moral experience which does not see it as a natural sign pointing to the existence of a deity.

What this raises, of course, is the general question of how to assess alternative readings of natural signs. Evans acknowledges that the signs are inconclusive and can be read differently, but he owes us a more extended account of what is meant by ‘reading’ and ‘interpreting’ here. Other philosophers have made use of the analogy with puzzle pictures such as the duck-rabbit, where the shift from seeing things in one way to seeing them in another way involves some kind of Gestalt switch. Evans alludes at one point to John Wisdom's famous article ‘Gods’ (7n), and this is another source on which Evans could fruitfully have drawn. Wisdom used the analogy with legal arguments, which may aim to bring out particular features of the facts in order to establish whether, for example, the defendant ‘exercised reasonable care’ or was ‘negligent’. Drawing our attention to features of our experience may enable us to see a pattern which we hadn't previously seen, although others may still say ‘I just don't see it’. Evans occasionally hints at this kind of account, and I would have liked to see it spelled out. One of the merits of his book is that it invites the atheist to take seriously the experiences which Evans sees as natural signs for God, and to come up with alternative interpretations of them, but that invitation would have been more enticing if Evans had said more about how to assess competing readings.

Instead he offers two things. In the final chapter he offers an account of why the natural signs could be seen as good evidence for God's existence. His strategy here is to distinguish between externalist and internalist epistemologies and to suggest what might be said from each perspective. He considers that the most plausible version of externalism would be some kind of reliabilism, and along those lines he suggests that natural signs could be seen as good evidence for God because they are the sort of evidence which tends to generate true beliefs. He acknowledges the obvious circularity but inclines to the view that epistemological circularity is unavoidable. Well, maybe, but whether the circularity is benign or vicious depends on how wide or narrow the circle is, and this one is about as tight a circle as one could get!

His internalist strategy is a principle of ‘phenomenal conservatism’: ‘we are prima facie justified in believing that things are as they seem to be. Those who “read” the signs as pointing to God's reality thus have prima facie justification for belief in God’ (182). He acknowledges that this is weak justification at best, and indeed it is. The experiences which he regards as natural signs may be enough to identify theism as a possible candidate for belief – in contrast to, say, belief in the famous Celestial Teapot. But that falls a long way short of being good evidence. Evans recognises that those who regard the natural signs as an overall justification for belief in God will have to deal with purported ‘defeaters’ such as the problem of evil. The trouble is that this seems to take us back to the terrain of argument, whereas what we need is some account of how and why someone might ‘read’ or ‘interpret’ the signs differently in the first place.

The other thing which Evans offers in lieu of this is what he calls the ‘Easy Resistibility Principle’. Yes, he says, the natural signs are inconclusive, but that's just what we should expect. God wouldn't want the signs of his existence to be compelling, because he wants us to ‘love and serve him freely’ (15). So the fact that the signs are inconclusive and easily resistible makes them all the more plausible.

This strikes me as something which even theists should see as hopelessly anthropomorphic. It invites us to ask ‘If I were God, what would I want?’ But how are we supposed to undertake this imaginative exercise? As Evans himself says in another context, ‘We simply do not know enough about what it would be like to be God to have any reliable intuitions about such matters’ (91). And again: ‘Since we are not God, we cannot be confident we know how we would relate to humans if we were’ (163). Attributing these all-too-mundane human desires and emotions to God is something which theists themselves should surely view with suspicion.

The Easy Resistibility Principle is in any case all too convenient. Consider someone who says: ‘I know that she loves me. She never tells me so, but she gives me occasional signs. And that's what you'd expect from someone who really loves you – that she would not force her love on you but leave you guessing.’ We would not say that this was someone who had good evidence. We would say that he was someone in the grip of self-deception.