There are three traditional arguments for the existence of God, two of which derive from our direct experience of the world and one which depends only upon the concept of God. These arguments have recurred in various forms throughout the history of philosophy: some were offered by Plato or Aristotle, most received their canonical form in the Middle Ages, and all were adopted or disputed by thinkers as eminent as Descartes, Hume and Kant. In various forms they have been revived in modern times and still represent a fruitful approach to understanding the rational basis of religious belief.
The ontological argument is the only a priori justification for God’s existence: that is, it does not depend upon our experience of the world to be verified, but instead relies upon purely logical inferences from the concept of God. It was adapted by Descartes in Meditation 5 and has been reformulated in recent times. The classical version comes from Anselm who addresses it to the fool in Psalm 14 who says in his heart, there is no God:
... this very fool, when he hears of this being of which I speak – a being than which nothing greater can be conceived – understands what he hears, and what he understands is in his understanding; although he does not understand it to exist. For, it is one thing for an object to be in the understanding, and another to understand that the object exists... Hence, even the fool is convinced that something exists in the understanding, at least, than which nothing greater can be conceived... And assuredly that, than which nothing greater can be conceived, cannot exist in the understanding alone. For, suppose it exists in the understanding alone: then it can be conceived to exist in reality; which is greater. Therefore, if that, than which nothing greater can be conceived, exists in the understanding alone, the very being, than which nothing greater can be conceived, is one, than which a greater can be conceived. But obviously this is impossible. Hence, there is no doubt that there exists a being, than which nothing greater can be conceived, and it exists both in the understanding and in reality. Proslogion 2
The argument starts from the definition of God as ‘a being than which nothing greater can be conceived’. The fool understands this concept but believes that such a being does not exist. If it did exist, however, it would be greater than the concept alone: an existing being is greater than a mere idea. Therefore the fool is contradicting himself as he can conceive of a being greater than ‘a being than which nothing greater can be conceived’, ie one that actually exists. Anselm’s argument is a reductio ad absurdum: assuming the premise that God does not exist leads to a contradiction. Therefore God must exist.
Another way of putting this is to say that God necessarily exists. If God is ‘a being than which nothing greater can be conceived’, then he must exist by necessity as such a being is greater than a merely contingent one. Since the concept ‘God’ contains the notion of necessary existence, then the proposition ‘God exists’ must be analytic, in the same way that ‘bachelors are unmarried’ is analytic: the predicate (exists, unmarried) is already contained in the concept (God, bachelor). Just as by definition it makes no sense to call a bachelor unmarried, so it makes no sense by definition to say that God does not exist.
There is clearly something wrong with such an argument, although at first glance it is not easy to see what. Kant’s famous objection was that existence is not a predicate: we do not add anything to a concept when we say that it exists, merely posit something in reality that corresponds to that concept. The concept remains the same: or, in Anselm’s terms, an existing being is not greater than a concept of that being – it just exists. The ontological argument plays tricks with the notion of existence, moving as it does from concepts to realities. What the fool has in his heart is a concept of a maximally great being that does not exist: if he replaces it with the concept of a maximally great being that does exist he does not need the being to exist for his concept to be coherent.
A contemporary of Anselm, a monk named Gaunilo, attempted to refute the argument on exactly these grounds. He described an island ‘more excellent’ than any other, and argued that since a real island is more excellent than a non-existent one, this island must by definition exist. In fact, it seems possible to ‘define into existence’ almost anything: certainly the argument can be used to demonstrate the necessary existence of the Devil (‘that than which nothing worse can be imagined’ – a real Devil is considerably worse than a mere concept) and any maximally great thing (islands, turkeys, Martians). In other words, Gaunilo’s island is itself a reductio ad absurdum as it shows that Anselm’s premise leads to absurd conclusions. However we define something, whether or not it exists is not within our power to arrange.
Such approaches focus upon the problematic idea of an analytic existential statement. Although Anselm believed that the statement ‘God exists’ is analytic, it clearly is not. The negation of an analytic statement creates a logical contradiction (such as ‘not all bachelors are unmarried’) – but as both Hume and Kant pointed out, ‘God does not exist’ is not a contradiction. Perhaps all that can be said is that if God existed, he would exist necessarily.
Alvin Plantinga has recently reformulated the ontological argument using modal logic: that is, defining concepts as necessary, possible or impossible. Briefly, there is a possible world in which there exists a maximally great being; maximal greatness implies existence in all possible worlds (ie necessary existence) as that is greater than merely possible existence; therefore such a being exists in our world (as it exists in all). This version of the argument is, at root, no different from Anselm’s: all it does is state that it is possible that a maximal being exists (itself a debatable claim); and that if such a being existed it would exist in all possible worlds. Whether it does or not is an entirely separate question.
To be fair to Anselm, the argument is presented more to assuage the doubts of believers than to convince the sceptics. Nevertheless, it is not logically valid and therefore fails as an argument. Perhaps, in the end, this is not surprising.
Unlike the ontological argument, the cosmological argument postulates God’s existence as an explanation of our experience of certain features of the world. The key feature invoked in this case is that of dependency. Things in the world depend on other things which in turn depend on others, and so on. The only way to stop an apparently infinite regress of dependency is to postulate something that does not depend on anything else. Such a self-sufficient being we call God.
In various forms the argument provided the first three of the Five Ways of Thomas Aquinas and was clearly considered by him to be the most persuasive form of reasoning.
... whatever is in motion must be put in motion by another. If that by which it is put in motion be itself put in motion, then this also must needs be put in motion by another, and that by another again. But this cannot go on to infinity, because then there would be no first mover... and this everyone understands to be God... it is necessary to admit a first efficient cause, to which everyone gives the name of God... if at one time nothing was in existence, it would have been impossible for anything to have begun to exist... Therefore we cannot but postulate the existence of some being having of itself its own necessity, and not receiving it from another, but rather causing in others their necessity. This all men speak of as God. Summa Theologica Part 1, Question 2, Article 3
So God ends the chain of dependency of things for motion, cause and existence by being the unmoved mover, the uncaused cause and – as the ontological argument also claimed – a necessary being. The same point follows from Leibniz’s principle of sufficient reason, which states that every fact has a sufficient reason to explain its being so. If we ask ‘Why is there something rather than nothing?’, the question seems to require an explanatory answer much like Aquinas’s God.
There are, however, a number of problems with this argument. Firstly, as David Hume pointed out, it seems illegitimate to reason from the part to the whole: the fact that every event in the universe has a cause does not entail the fact that the universe itself has a cause. Perhaps more significantly, even if a first cause were required to explain the existence of the universe, it is a huge step to identify that first cause as a recognisable God. Perhaps the prima causa was a team of gods, or a god that no longer exists; modern scientific thinking stops at some notion of a ‘Big Bang’, and modern understanding of time suggests that it makes no sense to ask what came before that; or perhaps the universe itself is in need of no further explanation – as Bertrand Russell said, “the universe is just here, and that’s all”. In any case, we are faced with the difficulty of using terms such as uncaused or necessary existence which, since we have no previous experience of such properties, may not be as clear or meaningful as they first appear.
Stephen Hawking begins A Brief History of Time by recounting the famous anecdote of an old woman who interrupted a scientist’s lecture (Hawking suggests it was Bertrand Russell but most versions say William James) with the words:
“The world is really a flat plate supported on the back of a giant tortoise.” The scientist gave a superior smile before replying, “What is the tortoise standing on?” “You’re very clever, young man, very clever,” said the old lady. “But it’s turtles all the way down!”
That memorable phrase – turtles all the way down – is often used as shorthand to refer to the problem of infinite regression that the cosmological argument raises. To postulate God as the solution to this regression is generally unsatisfactory and feels like special pleading. An argument which begins with the premise that every event is caused or moved by something else, ends with the assertion of an uncaused, unmoved entity. Of course, God is by definition a special case, but only a believer would be willing to accept such a leap. The cosmological argument may well identify a key problem (where and how did it all start?) but the argument’s solution to that problem is not at all convincing.
The argument from design states that the universe and its parts display evidence of order, regularity and purpose. Such qualities are also evident in the products of human design. Therefore, by analogy, the universe has a designer of enormous power, whom we may call God.
This argument is perhaps the most popular and enduring of all arguments for God’s existence. Kant described it as “the most accordant with the common reason of mankind” and this captures something of its fascination. As G K Chesterton put it:
... one elephant having a trunk was odd; but all elephants having trunks looked like a plot.
It appears as the fifth of Aquinas’ Five Ways and is to be found in Plato, Aristotle, Augustine and others. But its most famous expression was given by William Paley in 1802, using the common analogy of a watch:
... suppose I had found a watch upon the ground, and it should be inquired how the watch happened to be in that place... when we come to inspect the watch, we perceive... that its several parts are framed and put together for a purpose, eg that they are so formed and adjusted as to produce motion, and that motion so regulated as to point out the hour of the day; that, if the different parts had been differently shaped from what they are, of a different size from what they are, or placed after any other manner, or in any other order, than that in which they are placed, either no motion at all would have been carried on in the machine, or none which would have answered the use that is now served by it... the inference, we think, is inevitable, that the watch must have had a maker... every indication of contrivance, every manifestation of design, which existed in the watch, exists in the works of nature. Natural Theology I
Therefore, by analogy, the natural world must have a maker too. Like most versions of the argument, a great deal depends upon the use of analogy and the permissibility of inferring a cause from an effect. David Hume had identified exactly these problems a generation before Paley was writing, and his criticisms of the argument from design are generally considered highly effective. They appear in the posthumous Dialogues Concerning Natural Religion. In Dialogue 2 one of Hume’s characters, Cleanthes, gives a very plausible statement of the argument:
The curious adapting of means to ends, throughout all nature, resembles exactly, though it much exceeds, the productions of human contrivance; of human designs, thought, wisdom, and intelligence. Since, therefore, the effects resemble each other, we are led to infer, by all the rules of analogy, that the causes also resemble; and that the Author of Nature is somewhat similar to the mind of man, though possessed of much larger faculties, proportioned to the grandeur of the work which he has executed. By this argument a posteriori, and by this argument alone, do we prove at once the existence of a Deity, and his similarity to human mind and intelligence.
Hume’s criticisms of this argument are worth examining in some detail. He is concerned primarily with the relationship between a cause and its effect. Specifically, he argues that we cannot ascribe to a cause more qualities than are sufficient to produce the effect. So an imperfect world is only evidence for an imperfect creator; a finite world for a finite creator; an unjust world for an unjust creator; and so on. In Dialogue 5 he makes this point very memorably. By assuming in the designer only those qualities evident in the world as we experience it, a number of different inferences are perfectly reasonable:
Many worlds might have been botched and bungled, throughout an eternity, ere this system was struck out... why may not several deities combine in contriving and framing a world? This is only so much greater similarity to human affairs... In a word, Cleanthes, a man who follows your hypothesis is able perhaps to assert, or conjecture, that the universe, sometime, arose from something like design: but beyond that position he cannot ascertain one single circumstance; and is left afterwards to fix every point of his theology by the utmost license of fancy and hypothesis. This world, for aught he knows, is very faulty and imperfect, compared to a superior standard; and was only the first rude essay of some infant deity, who afterwards abandoned it, ashamed of his lame performance: it is the work only of some dependent, inferior deity; and is the object of derision to his superiors: it is the production of old age and dotage in some superannuated deity; and ever since his death, has run on at adventures, from the first impulse and active force which it received from him.
Hume rightly notes our tendency to assume that God has more and greater qualities than his creation: we ascribe perfection and goodness to God although neither are evident in the world as we experience it. Once we have given God these qualities, we tend to seek them back in the world and take for granted the existence of goodness, justice, purpose and so on, even though they are not apparent to us. This is not logic, of course, it is ‘fancy and hypothesis’ and the explanation for a number of oddities in religious thinking (notably the problem of evil).
But this is only the beginning of Hume’s attack. He goes on to note that the uniqueness of the universe (in the sense that it is the only one we know) makes any inference to a designer impossible. Only when two “species of object” are found to be constantly conjoined can we infer the one from the other: in the case of something so unparalleled as the universe, we cannot “form any conjecture or inference at all concerning its cause” (Enquiry §115).
For this reason, any analogy is bound to be flawed. The argument from design depends heavily upon analogies, and a number frequently recur: the world is like a house, like a ship, like a machine, like a wristwatch, like an animal, even like a vegetable. Of course, the choice of analogy is crucial: if the world is like an animal or vegetable then it seems likely that the guiding principle would be generation or vegetation, not the hand of a designer. Similarly, the analogy with a house or a ship implies a team of designers and engineers rather than a single divine architect. Each analogy brings with it assumptions about the world that inform the inferences drawn from that analogy: to compare the world to a watch is already to assume a watchmaker. A different comparison – particularly one drawn from the natural world – will lead to a different inference, and one such inference must be what Paley called ‘the operation of causes without design’, or what we refer to today as evolution by natural selection. The general acceptance of Darwin’s theory has put an end to the traditional form of the argument from design; at least, for all but the most religiously-minded thinkers. As Richard Dawkins puts it at the start of The Blind Watchmaker (a title designed to invert Paley’s analogy):
Paley’s argument is made with passionate sincerity and is informed by the best biological scholarship of his day, but it is wrong, gloriously and utterly wrong. The analogy between telescope and eye, between watch and living organism, is false. All appearances to the contrary, the only watchmaker in nature is the blind forces of physics...
In more recent times, the argument has surfaced in a slightly different format: what might be called the argument to design. This argument, put forward by Richard Swinburne and others, argues that we can recognise design and purpose not in biological organisms but in physical laws (thus side-stepping the ‘design’ accounted for by natural selection). Many scientists have observed how the universe seems fine-tuned to enable the sustaining of life, particularly with regard to the fundamental physical forces of electromagnetism, gravitation, and the strong and weak nuclear forces – even minor differences in these values would have resulted in a vastly different universe, one most unlikely to be hospitable to life. For Swinburne, this is an argument of probability: God is a more probable explanation for this fine-tuning than mere chance.
The exact degree of this fine-tuning is a matter of scientific dispute and many thinkers have doubted the validity of Swinburne’s conclusions. The mathematics are a little suspect: there are plenty of astronomically unlikely events that occur (eg being dealt a particular hand of cards at bridge) but which do not demand a designer to explain them. And even if a designer were a probable inference, such a complex being would itself require an account of its own complexity. As Hume saw, the problem of ‘who designs the designer?’ creates an infinite regress. And, in the end, perhaps it is not so surprising that we see such fine-tuned order in the universe: after all, if it were tuned differently we would not be here to observe it.
While none of the three classical arguments is conclusive, it has often been suggested that cumulatively they present a strong probability of God’s existence. Like leaky buckets, which when used together retain some water inside; or like a milking stool that is more stable with three legs than with two; these arguments, although individually unconvincing, together present a much stronger case. Such reasoning is logically doubtful – two poor arguments are no less poor when considered together – but there may be a psychological truth to the claim. More recent philosophy of religion has explored faith from a very different angle, one which does not require the support of strongly reasoned argument: to a pragmatist or fideist, for example, such rational concerns are of marginal interest.
It is also worth noting the common appeal to Occam’s Razor, the principle that explanations should be as economical as possible – or, more traditionally, that ‘entities should not be multiplied beyond necessity’. At first glance, it appears that God is a very economical solution to a number of problems. However, the economy is only apparent: a complex and intelligent being who is causa sui, unmoved, necessary, infinite, eternal and the source of both moral value and direct experience, may not be so simple a solution after all.