In this very stimulating book, C. Stephan Evans introduces the concept of a theistic natural sign (TNS) and defends the claim that such signs make it possible to have ‘natural’ knowledge of God's existence (knowledge that has not been acquired on the basis of religious experience or special revelation). Natural knowledge of God has long been thought possible. As Evans himself notes, traditional theistic arguments have been proposed to afford us such knowledge. However, Evans devotes this book to showing (a) that TNSs ‘lie at the core’ of these arguments; (b) that certain features of TNSs explain why these arguments are not conclusive and yet perennial; and (c) that TNSs have epistemic value in themselves: we may come to know (or have defeasible justified belief in) God by means of these signs non-inferentially, independent of any argument in which such signs feature.

In chapter 2, Evans explains his concept of a TNS, which is modelled on, but in some ways differs from, Thomas Reid's concept of a natural sign. A Reidian natural sign (RNS) is either a mental state (e.g. a sensation) or an extra-mental feature of the natural world, which is caused by a certain thing, functions so as to point us towards that thing, and leads us to form certain beliefs about it. RNSs facilitate our direct perception of a thing; a sign itself is not usually perceived, and no inference is made from the sign to that which it signifies. Likewise, a TNS is something – whether mental or extra-mental – caused by God, which gives us direct awareness of, and non-inferential belief in, God. However, as Evans notes, if God exists, everything is in some sense caused by God and could in theory point us to God, so there needs to be something more distinctive about TNSs. ‘What is needed, … is the idea not only that God is the cause of the existence of the sign, but that God created the sign to be a sign’ (p. 35). And, according to Evans, God has bestowed us with a (modifiable) ‘in-built tendency’ to read these signs correctly and to form theistic beliefs when we encounter them. Aside from being theistic, TNSs differ from RNSs being more easily resistible.

In chapter 1, Evans argues that we have good reason to believe these claims – that God would create easily resistible TNSs and provide us with a disposition to read them correctly. For we can reason a priori that if God existed and possessed the characteristics ascribed to him by traditional theism, he would make knowledge of himself widely accessible, in order to enable as many people as possible to participate in a fulfilling relationship with him. Evans calls this the ‘Wide Accessibility Principle’ (WAP). However, because such a God would want us to relate to him freely, and out of love, he would not be able to make such signs irresistible. Evans calls this the ‘Easy Resistibility Principle’ (ERP). Together, WAP and ERP explain why belief in God, though widespread, is not universal. Evans believes cognitive science of religion supports his view that we are naturally predisposed to form theistic belief, since it also makes this claim. (Though, of course, it doesn't concur that this predisposition is God-given.)

In chapters 3, 4, and 5, Evans hopes to cast new light on three types of traditional theistic argument by showing that different TNSs motivate each one. In Evans's view, cosmological arguments are underpinned by a sense of cosmic wonder, teleological arguments are supported by observed beneficial order in nature, and moral arguments are built upon our experience of human beings as having intrinsic worth, and our sense of moral accountability. According to Evans, each argument attempts to articulate its motivating sign, and thus inherits its force from the strength of that sign. Moral arguments, says Evans, are stronger than teleological and cosmological ones because the TNSs which lie in our moral experience point towards God more powerfully than, and have more informational content than, cosmic wonder and perceived beneficial order. Evans's thesis that ERP applies to TNSs (and so to those signs which underlie the noted arguments) requires him to maintain that none of these arguments is decisive. Thus, after giving a very balanced discussion of the merits and demerits of each argument-type, Evans ultimately concludes that all fail as conclusive proofs.

Despite the failure of these arguments – and I take this to be Evans's most significant original point – cosmic wonder, beneficial order, and our sense of moral worth can point us to God by themselves. The thought is this. The feeling of solidity one gets when touching a solid object, say, gives us direct awareness of, and non-inferentially justified belief in, the existence of a solid object. Likewise, our sense of moral obligation (providing this sign is ‘read’ correctly) can give us a direct de re awareness of, and non-inferentially justified belief in, God. In both scenarios, the move from the sign to the signified is psychologically immediate, so the belief formed in each case can be considered properly basic. (Evans, though, is keen to point out that TNSs may not be capable of giving us a clear or complete picture of God's nature. Rather, they point towards naturalism's being false and put us in a position to consider God's existence a ‘live option’.)

On the whole, the book is very clearly written; for this, Evans should be commended. However, one section of the book does lack clarity, and that is where Evans describes ‘cosmic wonder’. This term is given numerous characterizations, some of which conflict. To begin with, Evans says (p. 60), it ‘is a certain experience of the world, or objects in the world, in which they are perceived as mysterious or puzzling, crying out for some explanation’. Shortly after, he says it's our immediate perception of ‘the recognition that the universe is puzzling or mysterious’ (p. 61, emphasis added). In other places, cosmic wonder is described as the perception of the world as surprising (p. 60); as contingent (p. 62); and as having been created (p. 63). So which is it? The most charitable way to read Evans, I think, is to see cosmic wonder not as a perception of surprise, puzzlement, or mystery: these are not extra-mental properties the world has. (Even if they were, and even if they could somehow be perceived, since the world would not be puzzling or mysterious if God exists, mystery would not be there to be perceived.) Rather, we should see it as the feeling of amazement or awe at the sheer existence of the world, one which motivates us to ask ‘Why is there something rather than nothing?’ Evans himself suggests (p. 66) that some might find this the best way to understand the term.

Evans maintains (1) that at the time of experiencing cosmic wonder, we are not consciously aware of that which motivates it: ‘[O]n reflection we might cite various characteristics of that universe [its contingency, say] as the ground of the perception [sense of wonder], but the perception itself is immediate and primary’ (p. 61). However, this is not consistent with his contention that (2) our experience of cosmic wonder ‘is one in which we grasp the contingency of the objects around us … [one which] suggest[s] to us a kind of reality that exists in a deeper and stronger way’ (p. 69). The recognition of the universe, or of the things within it as contingent, says Evans, puts in our minds the idea of a necessary being and also suggests to us that the universe somehow rests on this being (pp. 62–63). Evans should drop (1). Sheer wonder itself is not sufficient to elicit belief in a necessary being. As is clear from Evans's own wording, to arrive at this belief, we need to be consciously believing or recognizing that the universe is contingent. We would not be pointed to the universe's dependency on a necessary being if we were not thinking of the universe itself as lacking this property. If cosmic wonder is to function as a TNS, then, it is crucial that belief in contingency be a psychological component of it.

This creates a problem for Evans. We can't sense that the universe is contingent: modal properties do not directly impinge on our senses. (Moreover, even if contingency were perceptible, so that contingency itself – a perceived extra-mental feature of the world – were functioning as a sign, one would then need to accept that contingency is caused by God. For, this is a necessary condition for being a TNS. Yet, that God causes contingency is a highly controversial thesis.) It seems, rather, that we arrive at the belief that the universe is contingent on the basis of certain inferences. Thus, Evans's claim that belief in a necessary being can be basic looks doubtful. For now it depends, not only on a belief, but an inferential belief. Evans could say that, although belief in the contingency of the universe is inferential, the move from that belief to belief in a necessary being is psychologically immediate. However, this would not be enough to support his thesis that belief in God can be gained independently of any inference.

Perhaps though, we could read Evans as suggesting that our sense of wonder gives rise to belief in a contingent universe. This would avoid us needing to perceive, or infer, contingency. However, that wonder could at once give rise to belief in the world as contingent, belief in a necessary being, and belief in the contingent world's dependency on this being, while not a conceptually incoherent suggestion, is one that appears, as a matter of psychological fact, plainly false: that this much is ever psychologically immediate looks doubtful. Further, this proposal seems to get things the wrong way round. One would not ask ‘Why is there something rather than nothing?’ if one were not already thinking that there might have been nothing. Cosmic wonder arises because we have in mind the thought that the universe is contingent, not vice versa.

In general, the analogy between TNSs and RNSs looks strained. Consider the signs that lie in our moral experience: our experience of ourselves as having moral obligations, and of others as having moral value. These experiences (sensations) are said by Evans not only to provide us with the immediate belief that we actually have moral obligations, and that humans actually have intrinsic value, but also that there is something that bestows us with such value, and to which we are accountable. In contrast, the feeling of solidity only directly gives rise to belief in a solid object; it does not give rise to a further belief about the source of that object's solidity.

One interesting question Evans briefly raises, and then drops, perhaps too swiftly, is whether there could be ‘negative natural signs’: signs that point to God's non-existence. Evans finds cause to answer negatively:

However, if God does not exist, evil must be a product of the naturalistic world. When encountered by us, evil and suffering could signify that the world is indifferent, naturalistic. So it's not the case that negative natural signs wouldn't be caused by the reality they signify. Furthermore, while it's a condition of theistic natural signs that they have an intended belief-producing function, the same is not true of non-theistic natural signs. The feeling of solidity, say, is not intended to make one believe there is a solid object in one's hand. Likewise, evil and suffering are not intended to produce unbelief. However, since none of these is a putative theistic natural sign (a sign of God's existence), these facts present no barrier to their being genuine natural signs. The possibility of there being negative natural signs, then, is one consideration that deserves further attention.

Another line of objection, one Evans himself examines in chapter 6, concerns whether ERP and WAP are reasonable. In particular, Evans questions whether WAP is too weak: isn't it more reasonable to think that God would make knowledge of himself universally available? Shouldn't cases of inculpable non-belief be impossible? Evans says it's ‘far from obvious that there are [such] cases’ (p. 161), but, even if there are, we can't be confident that God wouldn't have reasons for allowing them, since ‘our conceptual intuitions about such matters are surely defeasible, and, in some cases, highly uncertain’ (p. 162). However, in availing himself of this type of sceptical response, Evans undermines his own case for WAP and ERP. Evans arrives at these principles by asking what we should expect knowledge of God to be like, if God exists. Yet, if our intuitions about what God would do can't be trusted, then, while we can't be sure that theistic knowledge should be universally available, we can be no more sure that it should be widely available (and easily resistible). Evans's reliance on sceptical responses, here, and when dealing with objections elsewhere in the book, is in tension with his own argumentative strategy.

Moreover, even if we can trust our reasoning about such matters, it's not clear that we would arrive at ERP and WAP. What we should expect, if God exists, is that God would make it possible for all humans to enter freely into a fulfilling relationship with him, such relationships being achievable through loving and serving God. As Evans notes (pp. 13–14), the very reason God would make it possible for us to know him is to enable us to enter into such relationships. Yet, the possibility of freely entering into a fulfilling relationship with God would not be precluded if WAP were strengthened and ERP weakened. That is, knowledge of God being universally (not just widely) available, and signs of God being more coercive, would not force all persons to relate to God. Indeed, there are people who, while claiming to know God, do quite the opposite of serve God, and thereby turn away from him through their actions. Since one of Evans's theses is that WAP and ERP account for the inconclusiveness and persistence of the theistic arguments, it is crucial that he finds a way to rebut this line of objection.

Evans has here made a valuable and original contribution to the field of religious epistemology. Natural Signs and Knowledge of God deserves attention from, and is sure to provoke lively debate between, philosophers of religion and theologians. However, it should also be of interest to, and accessible to, anyone concerned with theistic apologetics. Even someone with little grounding in these issues is likely to gain something from it.