In the philosophy of mind there are a number of powerful arguments that demonstrate consciousness cannot in principle be explained on a physicalistic ontology. In other words, presupposing that mindless particles organised in various ways by mindless forces is all that exists leaves us without the explanatory resources to account for our mental life. Most of these arguments examine some basic property of consciousness (qualia, intentionality, etc.) and give an a priori proof that each is insusceptible of psychophysical reduction. And if the mind cannot possibly be reduced to the brain then mind and brain are not identical. Some form of substance dualism is implicated. [1]

The Conceivability Argument for Substance Dualism is different: It demonstrates through natural reason that the mind and brain are nonidentical without reference to any particular property of consciousness. In what follows I will be summarising the discussion provided by Edward Feser in Philosophy of Mind: A Beginner’s Guide. The argument begins with a few preliminary precepts.

Physical Impossibility vs. Metaphysical Impossibility

Feser first introduces a distinction between two kinds of impossibility: physical impossibility and metaphysical impossibility. It is helpful here to think of this as a distinction between strong and weak forms of impossibility. A state of affairs is merely physically impossible if, though impossible in the actual world, we can give a description of it obtaining in some possible world without contradiction. [2] In this connection consider the proposition,

A man survived a headlong fall from the top of the Empire State Building.

This proposition is merely physically impossible because we can describe a possible world (say, one with very weak gravity) in which such a thing is possible. By contrast, a state of affairs is metaphysically impossible if it is impossible in the actual world and we cannot give a description of it obtaining in any possible world without contradiction. In this connection consider the proposition,

A married bachelor drafted a square circle.

This proposition is metaphysically impossible because we cannot coherently describe any possible world in which such a thing obtains.

From this distinction we can derive a terse precept,

Conceivability entails metaphysical possibility.

A Related Principle of Identity

Let us now use this distinction to articulate a principle of identity: A is identical to B if and only if it is metaphysically impossible for A to exist apart from B; that is, only if we cannot conceive of any possible world in which A exists apart from B. Consider the claim that water is identical to H₂O. If you can conceive of a possible world in which you have water without H₂O, or H₂O without water, then, sensu stricto, water and H₂O are not identical but different substances.

Applying this Principle of Identity to the Mind and Body

Let us finally apply this principle of identity to the mind and body. If one can conceive of a possible world in which you have a mind without a body then mind and body are not identical. And indeed one can conceive of such a possible world. W. D. Hart, for instance, invites us to imagine a man who wakes up one day and shuffles sleepily into the bathroom to wash his face. Looking in the mirror, he sees two empty sockets where his eyes should be. With a hacksaw, he then removes the top of his head and discovers that he has no brain. In a panic he removes his head, his neck, his torso. At last his body is completely disposed of and he sees nothing in the mirror but the wall behind him. Of course, all of this is physically impossible but it also conceivable and therefore metaphysically possible.

W. D. Hart’s example is appealingly ghoulish but there are many other ways to conceive of mind and body existing apart from one another. Solipsism is another example. Out of body experiences a third. All of them are eminently conceivable. And from each of them it follows, ex hypothesi, that mind and body are not identical.

An Objection from Opponents of Substance Dualism

Against this, some opponents of substance dualism have argued that it is possible to conceive of two identical substances existing separately. For example: Water is identical to H₂O. But now let there be a substance having the properties of liquidity, quenching thirst, freezing at low temperatures, etc. whose chemical composition is X_YZ. If this is conceivable, then it is metaphysically possible; and if it is metaphysically possible, then A and B can be identical and conceived to exist separately and so the operating precept is violated.

Kripke’s Objection to the Objection

However, Kripke, the American logician, fussily dispatches this objection. Let water be that substance which in every possible world has those properties which water has in the actual world; i.e., liquidity, quenching thirst, freezing at low temperatures, etc. Let H₂O, meanwhile, be that substance which in every possible world has that chemical composition which H₂O has in the actual world. Trivially, the substance in the actual world having the properties of water is the same substance in the actual world having the chemical composition H₂O. But since “water” in any given possible world is the same substance having the properties of water in the actual world, and the substance having the properties of water in the actual world is H₂O, so the substance having those properties in every possible world is H₂O. And so water and H₂0 are identical in every possible world.

In other words, to conceive of a substance similar to water that is not H₂O is not to conceive of water existing apart from H₂O but simply to conceive of a substance similar to water that is not water. The case of water and H₂O does not therefore offer a counterexample to the test for metaphysical identicality. And so, we may conclude, the Conceivability Argument for Substance Dualism obtains.

A Final Point

As a final point it is worth noting that nonconceivability does not necessarily entail metaphysical impossibility. In other words, it does not follow from the fact that we cannot conceive of A existing apart from B that A and B are metaphysically identical. Maybe we just aren’t creative enough or intelligent enough to conceive of how it is possible. But conceivability of separateness does entail metaphysical nonidenticality—which simple precept does all the work of the argument. And unless the physicalist can demonstrate that that precept is wrong, substance dualism intrudes upon and falsifies his physicalistic ontology and the shadow of theism begins to darken his door.

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[1] See my discussion of the Argument from Consciousness here.

[2] It is important to understand that in this discussion “a possible world” is not another planet or a parallel universe. In modal logic a possible world is just a comprehensive description of a possible reality where “possible reality” is analogous to “hypothetical state of affairs” with the added condition that its description entails no logical contradictions. And just as there are infinitely many sets in set theory, so there are infinitely many possible worlds in modal logic.

Introduction. One of the most famous objections to the existence of God is that the joint claims that God is morally perfect and omnipotent are incompatible with the existence of evil and suffering. For if God were all good, the argument goes, he would want to prevent evil and suffering; and if he were all powerful, he would be able to do so. Therefore evil and suffering prove one of three things: That God does not exist, or that he is not all good, or that he is not all powerful. In short: The existence of an all-loving and all-powerful God is improbable given the obvious general fact of human suffering. 

Definition of Terms. Before responding, I need to briefly define a few terms that will be of use in what follows. “Free will” is the power of an agent to perform actions that are influenced but never fully determined by forces external to himself but of itself free will does not necessarily entail the capacity to do evil. God could, for instance, give us free will but constrain its exercise to the choice between different but equally good actions. I will therefore use the term “moral liberty” for the power of an agent to exercise his free will in making choices between good and bad actions; and “moral evil” for the use of moral liberty to perform bad actions. Finally, I will use the term “natural evil” for suffering having causes unrelated to moral evil—the suffering caused by natural disasters, accidents, diseases, and so on.

1. Moral Evil. To see why the problem of evil fails to disprove theism we first need to understand omnipotence in a more careful way. Theologians have always understood omnipotence to mean the power to perform any logically possible action. To note that God could not create a square circle imposes no limit on his powers because creating a square circle is not an action whose difficulty lies in the brute force required to perform it. In fact, it is not an action at all; rather, the imperative Create a square circle is a logically incoherent combination of English words which have no referent in the set of all logically possible actions that belong to omnipotence.

The relevance of this point to moral evil should be immediately obvious. It is logically impossible for God to create agents with moral liberty and ensure that they do not sin. The potential for moral evil is therefore an unavoidable consequence of moral liberty.[1] The question that needs to be asked is whether moral liberty confers any significant benefits upon mankind; and if it does, whether those benefits outweigh the suffering that it entails. In the following paragraphs I will be arguing that it confers upon mankind very significant benefits indeed; namely, that it makes possible the attainment of virtue, the formation of moral character and the capacity for genuine love. 

1.1 The Attainment of Virtue. To understand the importance of moral liberty to virtue, imagine a world from which moral liberty has been removed; in other words, a world in which the only possible exercise of free will is in the choice between different kinds of equally good actions. The result would be a toy universe or pleasure park in which we exist like animals or small children—experiencing comfort and sensory pleasure but without the opportunity to show empathy, courage, patience, self-sacrifice, forgiveness or heroism.  Such thought experiments help to bring out an important moral distinction between innocence and virtue. Innocence is a mere ignorance of evil; virtue requires that one face a significant choice between good and evil and freely choose the good. And since it is logically impossible for God to force us to freely choose the good, any world in which virtue is attainable is a world in which moral evil is a distinct possibility. 

1.2 The Formation of Moral Character. Because we have moral liberty we are continuously faced with the choice between performing good and bad actions. And, as Swinburne notes, humans are so made that when we choose to do good, it becomes slightly easier to choose to do good again at the next opportunity; and when we choose to do evil, it becomes slightly easier to choose to do evil again at the next opportunity. In this way, over time, we are able to change the desires that influence us and form either a very good or a very bad character. Without moral liberty our characters would have and unwaveringly maintain whatever measure of good or evil God elected at our creation and would therefore be completely devoid of moral significance.

1.3 The Capacity for Genuine Love. Love that is induced through the use of potions, hypnotism or spells is not considered genuine. For love between humans to be genuine, it must be freely given. It follows from this simple truth that any world in which genuine human love is a possibility is a world in which moral evil is a possibility. And this is because if you are truly free to give love you must be truly free to withhold it—even in situations where withholding it would be wrong. For a mother’s love for her young children to be genuine, for example, it cannot be forced upon her from above by God; it must be freely given and in that case it must be logically possible for her to withhold it—and so, perhaps, to neglect and abuse her children. All this holds equally for our love of God. To be genuine a love of God cannot be built into us by God. It must be freely given and this entails the freedom to withhold it.[2]  

Moral liberty therefore confers the profoundest imaginable benefits upon mankind. It provides us with the opportunity to attain virtue, form a moral character, and experience genuine love for each other and for God. It is not at all incoherent to suppose that a perfectly good person would choose to create a world in which these supreme goods were possible—even at the cost of moral evil.

2. Natural Evil. In discussing natural evil it is important to recognise that the suffering it entails is often bound up with moral evil. Cheaply built and poorly planned towns, for instance, can significantly raise the death toll during earthquakes and floods; the misuse of certain chemicals can significantly increase the incidence of cancer; the failure of wealthy countries to provide aid to poor countries can result in preventable famines—and so forth. Nevertheless, there is a great deal of suffering on Earth for which no human agent is responsible. And in what follows I will be arguing that such natural evil fulfils three additional and important purposes which moral evil alone could not fulfil: It ensures that opportunities to obtain virtue are universal; it broadens the scope and significance of our moral choices; and, most importantly, it conduces to the religious life.

2.1 It Makes Opportunities to Obtain Virtue Universal. In the section discussing moral liberty, we saw that empathy, courage, patience, self-sacrifice, forgiveness and heroism are all states contributive to virtue. But it needs to be noted that it is not moral liberty alone, but moral liberty and moral evil together, that provide an opportunity to manifest these virtues. In other words, only if someone eventually exercises their moral liberty to assault or abuse you can I exercise mine to show you empathy; only if you are robbed can I make personal sacrifices to provide for you. The question arises whether moral evil alone would afford adequate opportunities for everyone to form a virtuous moral character. In this connection Swinburne writes,

You can show courage when threatened by a gunman as well as when threatened by cancer; and show sympathy to those likely to be killed by gunmen as well as to those likely to die of cancer. But just imagine all the suffering of mind and body caused by disease, earthquake, and accident unpreventable by humans removed at a stroke from our society—no sickness, no senility, no bereavement in consequence of the untimely death of the young. Many of us would then have such an easy life that we simply would not have much opportunity to show courage or, indeed, manifest much in the way of great goodness at all. 

Consider a world without disaster, disease and decrepitude; a world in which the only cause of injury and death is, respectively, assault and murder. It is a mathematical certainty that such a world would provide far, far fewer opportunities for virtue and highly probable that some people would have no such opportunities at all.

2.2 It Broadens The Scope of Moral Liberty. Moreover, with careful reflection it is apparent that the removal of natural evil would also considerably constrain the scope and significance of moral liberty. For instance: The knowledge that poison causes death is unobtainable unless someone is first observed to have accidentally died by poisoning. And knowledge of poisonous toadstools and berries thereafter affords us an opportunity to exercise significant moral liberty: We can use that knowledge to kill off a neighbouring village by poisoning its well or to warn the neighbouring village not to eat toadstools. Earthquake belts, to give another example, give us a choice between building upon them cities that may be destroyed long after we are dead or avoiding doing so. Pathogens give us a choice between making biological weapons that kill thousands or developing antibiotics that save thousands. These examples show that natural evil broadens the scope and significance of our choices so that they are able to benefit or harm others far from us in both time and space. This confers on us a solemn moral responsibility and significance and so plausibly conduces to the aims of a morally perfect creator for his creatures. 

2.3 It Conduces to the Religious Life. If God exists he is the consummation and source of all power, knowledge, wisdom, beauty, rationality and love lying at the very heart of reality. A genuine and eternal love relationship with God is therefore the greatest conceivable good available to us. The question arises: Does a world that contains moral and natural evil conduce to the greatest number of creatures freely seeking the greatest conceivable good available to them? Reason and experience suggest that the answer may be yes. Pleasure and comfort are good and our world, of course, provides both. But a life that offered nothing else would make us complacent, hedonistic, idle and shallow. Suffering and death, on the other hand, force us all to confront questions about the ultimate meaning of life and so, for very many, plays a causal role in developing a relationship with God and living a religious life. 

Conclusion. The objection from evil seems ultimately to rest on the naive assumption that God created the universe to serve as a comfortable habitat for his human pets. However, we have seen that moral and natural evil are an unpreventable feature of any world in which the supreme goods of virtue, moral self-determination, genuine love and knowledge of God are significantly and universally attainable. It is probable that the creation of a pleasure park inhabited by creatures who know endless pleasure and comfort but are devoid of moral and spiritual significance would be a morally good act. But it is not at all incoherent to suppose that, viewed under the aspect of his infinite intelligence and moral perfection, God would know that the creation of a world precisely like ours is a morally better act. This is the so-called “Higher-Order Goods” solution to the problem of evil. Pleasure, innocence and comfort are good; but virtue, moral significance and love are goods of a higher order. And God, being perfectly good, wants to give us the very best things He has to give.

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[1] To create agents with moral liberty and constrain them from moral evil is simply to deny them moral liberty. It is logically possible, though hugely improbable, that a planet of agents with moral liberty will by chance alone contain no evil. But, needless to say, this state of affairs does not obtain on our planet

[2] The question arises whether God can freely withhold his love and if not then how, given my argument, it can be genuine. However, the difficulty only arises in the case of finite persons created by God for the purpose of knowing and loving him and each other. For if God created us with an immutable and irresistible love for himself and each other, that love would have its origin in something external to ourselves—namely, God—and would not therefore be freely given and genuine. But since God’s love is past eternal and has no cause external to himself, it is genuine even though by a necessity of his divine nature he is incapable of withholding it.

The so-called “minimal facts” are four facts about Jesus and the early Church that are accepted by the vast majority of critical scholars with terminal degrees in a relevant field. As such they form the “explanandum” or “thing to be explained,” in any informed and responsible discussion of what occurred on the first Easter Sunday. The minimal facts are,

Crucifixion and Burial. That after his crucifixion and death under the governorship of Pontius Pilate, Jesus was buried in a tomb by one Joseph of Arimathea.

The Empty Tomb. That days later the tomb was found to be empty by a group of Jesus’ female followers.

The Post Mortem Appearances. That thereafter various individuals and groups, at various times and places, had experiences that completely convinced them that they had seen, touched, spoken to and eaten with the risen Jesus.

A Sincere Belief in the Resurrection. That these experiences completely transformed the disciples, inspired a belief among them that God had raised Jesus from the dead and led to the formation of the Church.

Before weighing up the different hypotheses that have been put forward to account for these four facts, it is important to understand how they have come to enjoy such widespread assent among critical scholars.

Criteria of Historical Authenticity

Anyone can claim anything in writing—a point which applies to modern authors and, a fortiori, ancient authors since in the case of ancient authors we cannot appeal to contemporary eyewitnesses. On what basis, then, can we affirm that one historical claim is more likely to be true (or more likely to be false) than another? It is here that critical scholars apply what are called “critieria of historical authenticity.”

Before listing these it is important to first note that they state sufficient but not necessary conditions of historicity; in other words, that one or n number of criteria apply to p is further reason to regard p as historically authentic but that only one or none of the criteria apply to q is not a reason to regard q as historically inauthentic. It should also be borne in mind that they are not infallible guides to authenticity; rather, we should regard them as “Indicators of Authenticity.” We could summarise all this by just saying that the probability that some saying or event in the New Testament is historical is greater for its satisfying the criteria than it would be if it did not.

Early Multiple Attestation

According to this criterion the historicity of p is more probable if p appears in early, multiple and independent sources near in time and space to the alleged occurrence of p. It applies at many points to the New Testament of which I will give just one example here. The Resurrection appearances are multiply attested in Pauline and Gospel sources and were quickly proclaimed by the first Christians in the very city where Jesus had been crucified and buried. In his first letter to the Corinthians Paul says that the risen Jesus was seen by as many as five hundred witnesses at one time—and adds that many of those witnesses are still alive to be questioned. If Paul made up this claim and then announced it in the place where, within living memory of his audience, it was alleged to have occurred, he would have been exposed as a fraud. This gives us further reason for thinking that it is historically reliable.

Attestation has particular force when it originates in a hostile witness and we see this throughout the New Testament also. To again give just one example: The Sanhedrin, the Jewish court which engineered the crucifixion of Jesus, responded to the Christian claim that he had risen from the dead by accusing the disciples of stealing the body. This is an incidental admission from hostile witnesses of a fact that actually corroborates the Resurrection Hypothesis; namely, since the Sanhedrin would certainly have produced the corpse of Jesus if they could, the accusation strongly suggests that the tomb of Jesus was empty which is precisely what the Christians claimed a group of women had discovered on Easter morning. As Paul Maier notes, “if a source admits a fact that is decidedly not in its favour, the fact is to be presumed genuine.” 

Dissimiliarity

This criterion states that the historicity of p is more probable if p is dissimilar to the prior beliefs of those claiming its occurrence. The death and Resurrection of Jesus satisfy this criterion very clearly: Since first century Jews expected a Messiah who overthrows the Roman occupiers and a general resurrection at the end of history, a Messiah who dies and is individually resurrected in the middle of history represents a very strange and dramatic mutation within the Jewish worldview. N. T. Wright makes this point central to his massive study The Resurrection of the Son of God in which he argues that only the Resurrection itself can satisfactorily account for the emergence of a sincere Jewish belief in a dying and rising Messiah. The historicity of the New Testament claim that Jesus rose from the dead is thus highly probable on the criterion of dissimilarity.

Embarrassment

The criterion of embarrassment states that the historicity of p is more probable if p is problematic for the one who claims the occurrence of p—on the logic that an author fabricating a claim does not fabricate a detail that undermines the credibility of his own claim. It applies to many New Testament claims but to none more obviously than the crucifixion of Jesus. Prior to the Resurrection the Apostles had believed that Jesus was the Messiah prophesied to defeat the foreign occupying power and restore the throne of David in Jerusalem. His ignominious execution by the very foreign power his followers expected him to overthrow was therefore a profound embarrassment: It dashed their hopes of his triumph and appeared to confirm the Sanhedrin claim that Jesus was a false prophet accused by God. On the criterion of embarrassment the historicity of the crucifixion is highly probable.

The Criterion of Embarrassment applies again to the burial of Jesus. To appreciate this it is enough to know that Joseph of Arimathea, the man who both supplied the tomb and buried Jesus in it, was a member of the Sanhedrin; and the Sanhedrin was the Jewish court which had engineered the crucifixion of Jesus. If the Gospel authors wished to fabricate a story about the death and burial of Jesus they would not have given the Sanhedrin the dual role of murdering Jesus and then humanely laying him to rest. According to John A. T. Robinson of Cambridge, the entombment of Jesus by Joseph of Arimathea is, “one of the earliest and best attested facts about Jesus.”

It also applies to the discovery of the empty tomb by specifically female followers. And this is because, in first century Jewish culture, the eyewitness testimony of women was held in such low esteem that it was not permitted in a court of law. It is for this reason highly improbable that the Gospel authors would have hung a pivotal event in their story on the testimony of those witnesses least likely to be believed. The criterion of embarrassment suggests that both these inconvenient details—the burial of Jesus by a member of the Sanhedrin and the discovery of the empty tomb by a group of female followers—are truths reluctantly but dutifully recorded.

Historical Congruence

This criterion states that the historicity of p is more probable if p coheres with known historical facts about the context in which p is said to have occurred. This criterion applies at many points of the New Testament of which I will mention just one: The New Testament claims that Joseph of Arimathea requested the body of Jesus from Pilate so that he could bury it before the Sabbath; that Joseph and Nicodemus together bound the body in linen and placed it in a hewn tomb; and, finally, that when the Sabbath was over a group of female followers of Jesus arrived at the tomb with spices to anoint the body. Because all of these details are congruent with our knowledge of Jewish burial customs in the first century the criterion of historical congruence gives us further grounds for affirming their historicity. 

Semitisms

This criterion states that the historicity of a New Testament sentence p is more probable if it contains traces of an Aramaic or Hebraic origin. Since the New Testament was written in Greek and Jesus spoke Aramaic, traces of Aramaic in the Greek of the New Testament argue in favour of a primitive tradition that originates in Jesus. We see this, for example, in Paul’s quotation of a creedal tradition in Corinthians. “I delivered to you,” he reminds the Corinthians, “what I also received,” suggesting the transmission of an oral tradition. Paul then recites a list of eyewitnesses to the risen Jesus which, as Habermas and Licona point out, contains numerous hints of an Aramaic origin that would seem to vouch for its authenticity—including the fourfold use of the Greek term for “that,” hoti, common in Aramaic narration, and the use of the name Cephas (“He appeared to Cephas”) which is the Aramaic for Peter.

 Whatever hypotheses one defends will have to account for the four minimal facts mentioned above. And while I think it can be demonstrated almost beyond dispute that the Resurrection Hypothesis is an inference to the best explanation here, that is a topic for another post.

It is said that all philosophy begins in wonder; and Leibniz was surely right in insisting that the most fundamental thing to wonder at is why anything exists at all. “Why,” he asked, “is there something rather than nothing? This is the first question which should rightly be asked.” Even if it turns out to be unanswerable, the question is certainly reasonable. Everything that exists (from protozoa and poets to planets and parrots) has an explanation of its existence. It would be very strange indeed if, meanwhile, there were no ultimate explanation for the totality of things that comprise the universe.

However, in seeking ultimate explanations a philosophical riddle emerges—even if we constrain our focus to the ultimate explanation for the existence of a single thing. For we observe that all things owe their existence to some prior thing and we know that the series of causally interrelated things is either infinite or finite. But if the series is infinite, then there is no beginning to or explanation for it; and if the series is finite, then it must come to a stop at some first self-existent thing which, strangely, will not owe its existence to any prior thing. A number of different philosophers and thinkers in a number of different times and places have pondered this riddle and concluded to the necessity of an originating cause of everything in God. [1]

On superficial inspection, one might be tempted to object to the above line of reasoning as follows: If everything that exists needs an explanation, then God needs an explanation; and if God doesn’t need an explanation, then why does the universe need an explanation? The Cosmological Argument seems to come to grief on the child’s question, “Who created God?” 

Leibniz attends to this issue by pointing out that all existent things can be classified into two broad types: contingent things and necessary things. 

A “contingent thing” is the most familiar of the two: a thing whose existence is explained by, or contingent on, something external to itself and which could, in principle, have failed to exist. All manmade objects are like this. They owe their existence to whoever created them and it is conceivable that whoever created them could have failed to do so or chosen not to do so. We can easily conceive of a world in which Rembrandt did not paint The Night Watch or a world in which a particular teacup in your kitchen cupboard was not manufactured.  You and I, likewise, are contingent: Our parents might never have met or might have chosen not to have children. And things in the natural world, too, such as starlings, sapphires and stars, seem to fall into the same category: It is plausible to think that the universe, having developed differently, could get along without them.

A “necessary thing,” by contrast, is a thing which exists by a necessity of its own nature in every possible world. Many philosophers think abstract objects (such as numbers, sets and propositions) exist in this way. The number 5, for example, is not brought into existence at a discrete moment in time by something external to itself: an integer between 4 and 6 just exists by logical necessity. Likewise “2 + 2” make “4” in every possible world. Unlike poets and paintings and planets, there is no possible world in which the truths of mathematics and logic do not obtain and so each contains within itself the reason for its own existence: It exists because its nonexistence is logically incoherent.

Leibniz formalised all this into his famous Principle of Sufficient Reason: Everything that exists has a sufficient reason for its existence, either in an external cause, or in the necessity of its own nature. This principle is widely recognized as powerful and intuitive. And is, moreover, the way every rational person already thinks—even in the most extraordinary of cases. Suppose that you saw an adult horse materialise out of thin air. You would first seek a physical cause (“It is the work of an illusionist”) or, failing that, a psychological cause, (“I am hallucinating”) or, failing that, a supernatural cause (“It is an act of God”). As a last resort, you might simply give up and admit that you don’t know the cause, whatever it is, but what you would never do is conclude that, “There is no cause.”

Unless it can be demonstrated that the Principle of Sufficient Reason is less plausible than its negation (unless it can be demonstrated that it is more plausible to believe that things can exist without a sufficient reason for their existence) we are rationally obligated to postulate a sufficient reason for the existence of the universe. The question arises whether, like an abstract object, the universe exists by a necessity of its own nature or whether, like a blackbird or a black hole, the reason for its existence is to be found in an external cause. 

But very obviously the nonexistence of the universe is not logically impossible. One can coherently imagine our universe being reduced to the size of a full stop and there is no known metaphysical precept or rule of inference preventing us from subtracting from reality that remaining atom of space, matter and energy. The universe is contingent.

Here a skeptic, conceding the point, might be tempted to appeal to the eternality of the universe. For if the chain of causation recedes into the infinite past, then one might argue with Hume that for each and every state of the universe q there is a prior state p which caused it, and so on, ad infinitum, with no state being left without explanation. However, multiplying the number of contingent things, even to infinity, fails to solve the problem.

Leibniz himself anticipates this objection and, in response to it, asks us to imagine a book on geometry that was copied from an earlier book, which was copied from a still earlier book, and so on, to eternity past. “It is obvious,” he says, “that although we can explain a present copy of the book from the previous book from which it was copied, this will never lead us to a complete explanation, no matter how many books back we go.”  Even given an infinite series of copies, we will always be left wondering why the contents of the geometry book duplicated in each copy exist to be copied; that is, we will still be left without a sufficient reason for the existence of the book. 

Or imagine a man who has never seen a train before and arrives at a crossing as a long freight train is filing slowly past. Intrigued, he asks what is causing the train to move and is told that the boxcar before him is being pulled by the boxcar in front of it, which is being pulled by the boxcar in front of it, and so on, down the length of the train. It is obvious that we have not given the man a sufficient reason for the movement of the train and that his question will remain unanswered even if we tell him that the boxcars are connected together in a circle. Or that the whole universe is cluttered with slow-moving boxcars all intricately interconnected. Or even that there are infinitely many boxcars. 

This analogy frames the problem in terms of a causal series but it can also be framed in terms of a simultaneity of causes. The rotation of meshing cogwheels in a watch cannot be explained without reference to a spring, even if there are infinitely many rotating cogwheels. 

In The Coherence of Theism, Oxford professor of philosophy Richard Swinburne finds and precisely articulates the problem under discussion: A series of causes and effects sufficiently explains itself if and only if none of the causes is itself a member of the collection of effects.  So: If the cause of a lamp lighting up is its being connected to a battery, and the cause of a second lamp lighting up is its being connected to a second battery, then the cause of the two lamps lighting up is accounted for—a principle that would hold even given infinite lamps and batteries.  But this principle cannot account for cases where each event is both the effect of a preceding cause and the cause of a succeeding effect. For if A causes B which causes C which causes D, then, strictly speaking, the cause of D is not C but A. In short: An infinite series of causally concatenated events is like infinite number of glowing lamps all wired together in a vast network in which a battery is nowhere to be found.  Appealing to an infinite regress of explanations and causes is finally no better than suggesting that, when it comes to the universe, there is no cause or explanation. Both responses violate the Principle of Sufficient Reason. 

Schopenhauer aptly dubbed such reasoning a commission of, “the taxicab fallacy.” The Principle of Sufficient Reason is a lynchpin of rational thought for atheist and theist alike and all a proponent of the Cosmological Argument is doing is inviting us to follow it out to its ultimate logical consequence. An atheist, seeing where the Cosmological Argument is leading, cannot simply dismiss the Principle of Sufficient Reason like a hired hack because it has already taken him as far as he is willing to go.

We have seen that denying that there is an ultimate cause and explanation of the universe (either simpliciter, or by appealing to an infinite regress of causes and explanations) violates the Principle of Sufficient Reason. It follows that we are obligated, on pain of irrationality, to postulate a terminus to the series of causes and explanations.  But why think that the terminus implicated is God or something like God? 

Just as it is possible to make inferences about a writer or painter from his or her artistic output, so it is possible to make inferences about a cause from its effect. And what can we infer about the cause of the universe from its effect? We begin to answer this question by asking another: What is the universe?  The universe is all existing space, time, matter and energy. And it follows by inferential necessity that the cause of the universe is an immaterial entity that lies beyond space and time. [2] Only two things fit this description: An abstract object and God. And abstract objects (the number 14, the set of all right triangles, etc.) are causally inert and so cannot possibly be capable of creating all of physical reality.  The entity implicated by the Cosmological Argument is therefore God, or something like God: a Necessary Being that transcends physical reality and is of unimaginable intelligence and creative power. 

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[1] Ancient Greek philosophers developed the cosmological argument into clear form. Christian, Jewish, and Islamic traditions all know it. And it can be found in African, Buddhist and Hindu thought as well. It is, moreover, studied and defended by contemporary philosophers and remains influential—in some cases, surprisingly so. Alasdair MacIntyre, for example, is recognized as one of the most important Anglophone philosophers of the 20th century. He claims that he converted to Catholicism, “as a result of being convinced of Thomism while attempting to disabuse his students of its authenticity.” (Thomism being the philosophy of Thomas Aquinas of which three versions of the cosmological argument are an integral feature). And the philosopher Edward Feser tells a similar story.

[2]  The Cosmological Argument is reducible to the proposition, If a contingent being exists, then a Necessary Being exists. Copleston argued that this is a logically necessary proposition but not, strictly speaking, an analytic proposition. And this is because it is logically necessary only given that there exists a contingent being, which has to be discovered by experience, and the proposition, A contingent being exists is not analytic. “Though once you know that there is a contingent being,” he emphasised, “it follows of necessity that there is a Necessary Being.”

[*] This is a shortened version of a longer discussion of the argument given here.