In defence of William Lane Craig

William Lane Craig, or 'Bill' to his mates.

William Lane Craig is a Professor of Philosophy at the Talbot School of Theology, Biola University. He is best known for his 'Christian apologetics', which has led him into combat with some of the world's most famous atheists and agnostics. However, he has become a much maligned figure in the public eye recently, and I have a few words to say in his defence.

Craig is often mischaracterized, usually by his ideological opponents, so it is necessary to take a few lines to detail what he has actually acheived in philosophy, and what sort of reputation he enjoys. Craig is an important figure in the philosophy of time (check back for more posts on this fascinating subject), where he has made notable contributions to defending ‘presentism’, a theory of time which holds that there is an objective present moment, and that past and future events do not exist. In fact, he has been important in the resurrection of this intuitive but philosophically problematic position, which appeared to have died a death around about about the 1960s. The problems associated with presentism do nothing to discredit Craig’s contribution to the theory, nor his detailed and wide-ranging critical studies of the two major theories of time, the A- and B-theories. (Presentism is a variant on the former).

As far as I am concerned, the above considerations do more than enough to anchor Craig’s position as a prominent figure in academic philosophy. However, when we move to religion, things get a little more hazy. Craig’s early approach to the philosophy of religion was a strictly academic one, and his book ‘The Kalam Cosmological Argument’ is still regarded as a leading work on that particular argument for God’s existence; so far, so good. On paper, Craig is also theologically credible, having studied under two of the most important theologians of the last 100 years - John Hick and Wolfhart Pannenberg. However, more recently, Craig has turned his attention to Christian apologetics, the defense of faith, and as such has come under fire. His ‘pastoral’ mission includes touring the Middle East with followers, writing self-help style books aimed at everyday Christians looking to defend their personal belief, and pursuing an obsessive debating schedule with just about every famous atheist and agnostic academic in existence. In aid of these aims, his promotional machine is a powerful force, pushing such debates in a manner that might be described as a little aggressive. Dawkins et al have taken pains to discredit Craig on these grounds, dismissing him as ‘a theologian’ (a term of abuse in Dawkins’ language), and ‘a professional debater.’

It’s sad that such criticisms conveniently seek to ignore Craig’s well-earned academic credentials, and the startling length of his list of publications (though quantity of work does not, alas, entail quality). Also frequently maligned is Craig’s debating style, which is sharp, sometimes rhetorical and verbally forceful; amusingly, he appears to have learned his lines well, since the content of his opening speech on anything God-related has remained identical for over 30 years (see the vast list of Craig’s videos on youtube). His opponents unfairly level the charge that Craig’s arguments take the form of logical trickery, designed to confuse and obscure to his popular but not intellectual advantage. But this is an easy criticism, and not a very clever one. The arguments Craig presents are just the standard theistic arguments for God’s existence; and the philosophical debates they raise are too lengthy and complex to properly assess here, or indeed in any public-debate environment. This is half the problem with any debate about God’s existence. We should therefore be careful not to confuse style with substance; Craig’s opponents confuse the idea that Craig is deliberately muddying the intellectual waters with obscurantism with the depth of the subject matter Craig introduces in support of his case. Granted, Craig is perhaps ill-advised to rehash one-sided arguments for God as ‘proofs’ for his case in public debates, but the problem is in this style of presentation, not the substance of the arguments themselves, about which there are often lively philosophical arguments to be had. The problem is that the chance of giving proper treatment to such debates in a public forum is slim; but the debates do exist nonetheless, and Craig has a right to raise them in his defence. In light of this, the claim of Andrew Copson, of the British Humanist Association, that Craig's arguments are 'easily refuted' outside public debate is particularly laughable. Copson needs to read some Plantinga.

I think, then, that I would generally defend WLC from his critics. He certainly has some crazy ideas, most often religious, which I could never accept, nor defend - his admission of faith over reason is worrying, as is his bold but unacceptable defense of certain biblical events. But these are propounded in the domain of Christian apologetics, which calls for crazy ideas to defend its often crazy claims! By contrast, in the domain of philosophy proper, Craig deserves respect, and this should also be shown in response to the philosophical arguments he calls upon in debate. Respect for an argument entails fairly engaging in the debate surrounding it, and not writing it off as nonsense before even properly considering it. Far from being a ‘professional debater’ or ‘crackpot theologian’, Craig is a distinguished academic philosopher, and this should not be forgotten in spite of his many unpalatable religious views, or his forthright debating style. Certainly, his philosophy is much more highly regarded by the philosophical community in general than the 'philosophy' of his most famous counterpart, Richard Dawkins; I'd probably echo the letter to Dawkins by philosopher of religion Daniel Came concerning the proposed debate between the two.

Really great introductions to philosophy

I thought that since this is a popular philosophy blog, I should at some point list some of the best popular philosophy books I've come across which serve as an introduction to the subject. I'll stick the list in the sidebar as well for future reference and keep adding to it.

What to read

- The Problems of Philosophy - Bertrand Russell. A bit dated in its theories (sense-data, anyone?), but still an excellent introduction by the man who was largely responsible for giving 20th Century philosophy the go-ahead.

- Think - Simon Blackburn. This is on everybody's list, but really does deserve a mention. Short and sharp, like James Randi.

- The Riddles of Existence - Sider/Conee. Great introduction to metaphysics (the study of the nature of reality) by two leading contemporary philosophers.

- The Making of a Philosopher - Colin McGinn. Another great 'intellectual autobiography' which conveys philosophy with enthusiasm is Brian Magee's 'Confessions of a Philosopher.'

- Meditations - Descartes. Perhaps the most important text in the history of philosophy for philosophy today, and remarkably clearly written even by modern standards.

- Philosophy Bites - Edmonds/Warburton. The series of podcasts on which it is based are outstanding.

The Ship of Theseus

The Ship of Theseus (but which one?)

The wandering adventurer of Greek myth, Theseus, has had many an epic voyage in his time, but has decided to call it a day. Among the possessions to be stored away is his magnificent ship, which has seen better days. Theseus asks his followers to repair the ship, and restore it to its former glory by replacing all the planks of wood out of which it is made. So one by one, the old planks are replaced by new planks, and then piled up in a heap. Finally, the work is done, and Theseus’ followers invite him to survey the restored ship. But something is not right; Theseus ponders a while, and then says ‘well, it looks very nice and all, but I don’t really see in what sense this is MY ship at all - for this is an entirely new ship, which has no material in common with my old, beloved vessel.’

The philosophical problem raised by this story is the following: if an object is replaced, part by part, until it is composed of a set of entirely new parts, is it still the same object? Here, we are using the example of a ship, but the problem is similar to the famous question of personal identity - since the majority of our bodily cells are completely replaced in the course of 15 or so years (let’s assume), in what sense am I the same person as I was 15 years ago? (Personal identity, it should be noted, is more complicated, since matters concerning consciousness and psychological continuity muddy the waters).

The issue in cases such as the Ship of Theseus is about persistence and parthood - that is, what it takes for the same object to exist over time, and retain its identity if its parts are changed. In the Ship of Theseus example above, the problem can be sharpened when we add to the story that Theseus’ followers took the old, replaced planks, and rebuilt the old Ship of Theseus exactly as it was before replacement. Now we have two ships - but which one is the ship of Theseus?

1. Consider the original ship. It was replaced, plank by plank, by new wood, and then rebuilt from the old planks. Perhaps this is the ship of Theseus, which simply disappeared out of existence, and then re-appeared again as soon as it was rebuilt. But this is absurd - for this leads to the acceptance that as soon as one plank was replaced, the Ship of Theseus lost its identity - either that, or it lost its identity arbitrarily at some point in the process, on account of one particular plank being replaced. This is obviously not true. If an object loses a part - for example, if a table loses a leg - then it is still the same table as it was before it lost the leg.
2. Consider the new ship. Perhaps this is the ship of Theseus. However, this cannot be, as we cannot say for definite at what point this new ship came into existence. Was it after the replacement of one plank? Two planks? The object that is made up of half old planks, half new planks (i.e. the ship halfway through repair) has a claim to be both the old and the new ship. And the new ship when completed shares no material with the old ship at all, which was the source of Theseus’ original concern.

This paradox arises because of the intuition that no single physical object can have two spatial locations at once. For this reason, we cannot simply say that both ships are the Ship of Theseus. It also seems odd to say that the original ship popped out of existence as soon as it began to be replaced. Metaphysical problems concerning the nature of an object’s identity, and to what extent that identity depends on physical make-up, are raised in consideration of this problem.

The Ontological Argument for God's existence

Nobody's claiming the argument proves THIS...

Ontological arguments seek to prove the existence of God simply by armchair reasoning - by thinking through concepts logically rather than venturing out into the world to find material evidence. Ontological arguments usually start from a definition, from which the existence of the entity logically follows. Here is one example:

1. By definition, God is a supremely great existent being
2. Therefore, God exists.

The argument is valid (see previous post). However, is it convincing? No. This is because only somebody who is independently prepared to admit the conclusion (2) will accept the premise (1). Therefore, we would say that the argument is ‘circular’, since the acceptability of the premise depends on whether we already believe the conclusion. Or rather, the argument assumes its own conclusion. Though valid, the argument doesn’t prove anything (though this guy might disagree).

Consider a more sophisticated version, attributed to St. Anselm of Canterbury (1033 - 1109):

1. God is the greatest conceivable being
2. If something is the greatest conceivable being, it possesses all great-making properties
3. A great-making property is a property that, if had, makes a being greater
4. Existence is a great-making property
5. Therefore, the greatest conceivable being possesses the property of existence
6. Therefore, God possesses the property of existence
7. Therefore, God exists

This new argument is valid. But is it sound, and therefore convincing to any degree? Though it is thought fashionable these days (mostly to people who haven’t studied any philosophy) to simply declare this argument absurd and walk away, this isn’t a rationally acceptable thing to do - reasons must be given for why an argument is unsound before we reject it.

The problem is that this argument cannot so obviously be declared false as the first one, since it is not so obviously circular. It’s all very well to assert ‘you can never define something into existence’, but this isn’t really pointing out a specific flaw in the argument, which is a harder task than many think. Whether this version of the Ontological Argument is good or not, it poses an interesting logical problem nonetheless, and has premises to which even the atheist can agree. Unfortunately, accepting the conclusion renders atheism incoherent.

I love ontological arguments - if you give them a chance (which you should), they are endlessly fascinating. More to come on this topic.

Soundness, validity, and life on Mars

In philosophy, an argument is valid if it is not possible that all the premises be true and the conclusion false. The following is the paradigm (often repeated) of a valid argument:

1. All men are mortal
2. Socrates is a man
3. Therefore, Socrates is mortal.

(1) and (2) are the premises, and (3) is the conclusion. In this argument, it is not possible that both premises be true, and the conclusion false. Therefore, the argument is valid. However, validity has nothing to do with the actual truth of the premises or the conclusion - it is to do with how the conclusion (whatever it is) relates to the premises.

Socrates

Validity by itself is not enough for an argument to be convincing. An argument also has to be sound. To be sound, an argument has to be valid, and in addition all its premises must be true. Whilst the above argument is valid, it is debatable whether it is also sound. Maybe we’d trivially disagree with premise (2), for example, and say that Socrates was a man, rather than is. If we disagree with a premise, we needn’t be committed to the argument’s conclusion. Soundness is therefore often a matter of judgment, whereas validity is not.

So to be convincing (i.e. a good argument), an argument must be valid, and it must also be sound. However, if an argument is valid, then that doesn’t mean that it has the potential to be sound. Consider:

1. I have a black cat
2. I don’t have a black cat
3. Therefore, there is life on Mars.

This is a valid argument (believe it or not). Remember that to be valid, it must be impossible that both premises are true and the conclusion false. This argument satisfies that definition, since it is impossible that both premises be true full stop, as they are contradictory. This yields what is sometimes called 'the principle of explosion' - the fact that (in classical logic at least), a contradiction logically entails every proposition. Needless to say though, only a complete nutcase would take this as proof that there exists life on Mars!

Philosophers are understandably wary of contradictions. By thinking about such cases, we can be more careful about using words like ‘valid’ as a means of persuasion in everyday conversation. Hooray!

Trolley problems

A train is rushing out of control down the track. 5 people are tied to the track, unable to get out of its way. If the train is allowed to continue, they will all be killed. Watching from a nearly signal-box, you are given an opportunity to influence the scenario. A pull of a lever will divert the train, and send it into a side-track, where there is only one person tied up. The five people will be saved; however, the one person will be killed if the train is diverted. Do you pull the lever?

From a utilitarian perspective, there is only one good answer - pull the lever, minimizing the cost to human life. The consequences are what matter, and in this case, pulling the lever will mean that 1 person dies instead of 5 people. However, a person may still have some worries about pulling the lever nonetheless - for in pulling the lever, you make yourself directly responsible for a person's death. Considered in isolation, removing the 5 people on the original track from the scenario, your act is equivalent to murder.

 Whether any human is 'stop-a-train fat' is a separate question...

The scenario can be tweaked to isolate differing moral intuitions in different cases. Consider:

1. The scenario remains the same, except that the single person on the side-track is your brother. Divert?
2. You stand on a bridge above the railway. There are 5 people on the track who will be killed by the train. However, the train can be stopped by pushing a fat guy standing on the bridge alongside you into its path, and then the 5 people will be saved. Push him? (most find this a harder choice than the original example).
3. The same scenario obtains as in (2), except the fat guy is a villain, who was responsible for the train being out of control in the first place. Push?
4. The same scenario obtains as in (2), except the fat guy is your brother. Push?

Discussion of these examples has been widespread in philosophy and online. The philpapers survey (see previous post) reported that almost 70% of philosophers would pull the lever in the original case.

I think I’d probably pull the lever in the original scenario, and push the fat bloke in both 2 and 3 (though the fact that he’s a villain doesn’t seem to affect things particularly). At least, I think doing these things would be the right thing to do, whether or not I had the courage to do them myself. However, the family cases raise some of the most profoundly difficult moral dilemmas in moral philosophy. It’s a tough question as to whether one’s personal relationships should affect one’s moral outlook in such tricky cases.

What philosophers think

A philosophical variant of Michaelangelo's 'The Creation of Adam.'

Philpapers.org conducted a survey a few years ago into the views of contemporary academic philosophers on a range of issues. The survey can be found here: http://philpapers.org/surveys/. In amongst the jargon, there are interesting findings to be had.

The survey shows that 72.8% of philosophers (faculty members, sample of nearly 1000) ‘accept or lean towards’ atheism, whilst only 14.6% ‘accept or lean towards‘ theism, the view that there exists a creator and sustainer of the universe. 12.5% were undecided.

What I find most interesting about the study is the correlative data - that is, taking views on a particular area and seeing how they correlate with views on a different area. You might expect, since ‘materialism’ these days is often used (misleadingly) as a synonym for ‘atheism’, that the vast majority of atheist philosophers are physicalists/materialists (see post - The Explanatory Gap). The survey shows this to be false. 67.9% of atheist philosophers call themselves physicalists, which leaves almost 20% who describe themselves as ‘non-physicalists.‘ (12% remained undecided on the issue, or refused to commit to either category).

Perhaps even more interestingly, 22.3% of theists call themselves physicalists, and thus commit themselves to the view that all that exists is physical matter. However, this is less contradictory than we might at first think - physicalism, construed as a view about human minds and the universe we inhabit, doesn’t rule out a God existing outside the universe, or a God not ‘existing' in the ordinary spatial sense. Nevertheless, the fact that 59.7% of theists are non-physicalists does indicate a predictable sympathy between the two views. Once you admit that there is mental stuff, I suppose you are less likely to find the notion of a non-physical being such as God suspicious for reductive reasons. (To say nothing of the role of the 'soul' in Christian religious thought).

Presenting ‘majority arguments’ as conclusively supporting a particular view (i.e ‘this view is true because the majority of people think it’) is a big mistake. We cannot conclude from the fact that 72.8% of philosophers are atheists that atheism is true - majorities can be seriously wrong in their views, as history has shown. Statistics should in any case be treated with caution. Nevertheless, the fact that a vast majority of philosophers are atheists is at least suggestive. Whether we draw any further conclusions here depends on how we view philosophers in general - are they skilled investigators into the fabric of reality, or just bearded men with weird views? Sadly, and most often unfairly, they are regularly seen by the public eye as falling into the latter category.

The firing squad

Imagine the following scenario. You are put before a firing squad as punishment for a serious crime. Ten expert marksmen are lined up, each with his rifle cocked and loaded, and pointing at your head. You grit your teeth, close your eyes, and prepare as best you can to face your seemingly inevitable demise. The roar of the ten rifles explodes in your ears...

... but you’re still alive. Gingerly, you open your eyes to discover, to your amazement, that all ten expert marksmen have missed the target completely. Similarly astonished, the leader of the squad decides, in a fit of sympathy, to let you walk free.

Given time to reflect on what has happened, two options present themselves. The first would be to, quite rightly I think, demand an explanation for why the extremely unlikely scenario you just endured happened in the first place. The second would be to shrug your shoulders, think nothing more of it, and then return to your life, putting the event down to mere coincidence.

Having decided, as any rational person would, to rule out blind chance and seek to explain the scenario, we are presented with only two possibilities. One is that a million different firings all took place on the same day as yours. If the chances of ten expert marksmen all independently missing the target are one in a million, then given a million firings, we would expect one to fail. It seems that yours was the one which failed; and though you are lucky, this isn’t so surprising, since we would expect one firing to fail anyway.

The second explanation, given that yours was the only firing taking place that day, is that something suspicious is going on. Either the marksmen were all told to miss, or they were equipped with blank ammunition, or something similar. There was intention/design behind the occurrence which explains why it happened.

The firing squad story presents a direct analogy with the existence of the universe. We know from science that the physical constants needed to produce a developed universe at all are ‘fine-tuned’ - that they had to fall within an infinitesimally small range of values (http://en.wikipedia.org/wiki/Fine-tuned_universe). The very existence of a stable, developed universe such as ours is inherently unlikely. Given this widely accepted view, and since it is not rational, given the odds, to put things down to chance here (as the firing squad analogy clearly suggests), we have two main options. A million universes? Or intention/design. The first of these is the ‘multiverse’, the hypothesis that our universe is one of many universes existing in parallel. The second option is...well...suggestive of something else; something quite different.

Many possible worlds

Though it's easier to imagine possible worlds like parallel universes,
there's actually nothing 'parallel' about them - they are disconnected.

A ‘possibility’ is a way the world might have been. So for example, if I were to say that ‘flying pigs are possible’, this is to say that our world might have contained flying pigs, if it doesn’t already. There’s nothing contradictory about the idea of a flying pig; and furthermore, there is nothing in the laws of nature that rules out the existence of flying pigs. The reasons why we think flying pigs don’t exist is that we have never observed them; but this doesn’t affect whether or not flying pigs are possible. There could be some somewhere.

We are comfortable talking about possibility in every speech, but philosophers go one step further. For every logical possibility, there is a ‘possible world’ in which that possibility is said to take place. Thus, to say that ‘flying pigs are possible’ is to say that ‘there is a possible world in which there are flying pigs.’ If flying pigs were discovered to actually exist, then the possible world just described would turn out to be the actual world. It follows that there ‘exists‘ a possible world for every conceivable possibility - including worlds in which the laws of nature are different to the actual world. Let your imagination run wild with the possibilities - for every imaginable state of affairs, there is a possible world in which that state of affairs takes place.

It’s natural to think that possible worlds talk is just a useful way of conceptualizing possibilities. We normally assume that there exists only one world - the actual world in which we live. However, some philosophers (a minority) go even further - they hold that all the possible worlds exist just as much as the actual world. On this view, there really do exist worlds with flying pigs, mutant humans, and angry Greek gods. There also exist worlds in which you live, but have a different hairstyle. Or have fourteen fingers.

Our world is thus one world among many. We call it ‘the actual world’ because it’s the one we happen to inhabit. But when spoken by all the other people in the other worlds (including other versions of you), the phrase ‘the actual world’ refers to their world. There is thus nothing to really distinguish our world as ‘more real’ than the rest. Where are all these other worlds? Well, they’re causally and spatially disconnected from each other - and so it is not possible for us to access them.

Why think that there exist an infinite number of real, disconnected worlds? It helps solve lots of other tricky philosophical problems. (You’ll have to take my word for it). The question is whether this benefit is enough to convince us of their existence, and the reality of weird and wonderful things like flying pigs and fourteen-fingered humans, in the depths of logical space.

(Not to be confused with the ‘multiverse’ - a scientific hypothesis about many universes all existing in a single possible world - our world).

The Philosophy Song

The Monty Python team approach the subject of philosophy in their typically amusing style. See also their 'philosophers' football match' - http://www.youtube.com/watch?v=ur5fGSBsfq8 .

Zombies

Zombies are dead behind the eyes, and stagger around seeking sweet, sweet brains. In the context of philosophy, the staggering around is less important - what philosophers focus on is the notion of a being lacking in conscious experience.

A ‘philosophical zombie’ is a being that physically exactly resembles a normal, healthy human being, but inwardly does not experience the conscious experiences that human beings ordinarily experience. Zombies can think, talk and act, but they do not experience sensations of colour, taste, etc. When we see a blue sky, or a red apple, we get a direct impression of blue-ness or red-ness - there is ‘something it is like’ to see a blue sky. This ‘what it is like’ element is a vital part of conscious experience. Yet the zombie, though it might claim that it has rich experiences of blue, and rich tastes of sweet and sour, does not experience these experiences. It is brain-dead in the sense that there is nothing going on inside its head in terms of conscious experience. The main thing to note is that the zombie is identical to any other human being in terms of physical constitution - but lacks rich conscious experiences of things such as colour, sound and taste.

Daniel Dennett claims that consciousness
is largely an illusion. Perhaps this is
because he is a zombie. (Chalmers)

A thought experiment using zombies seeks to demonstrate the conclusion that there is more to 
the physical world than simply physical stuff - that consciousness indicates that there is also mental stuff. (See previous post: the Explanatory Gap). Though zombies probably do not exist in the actual world, the idea of a zombie seems possible - it seems like a possibility that zombies could exist in the real world, though if they did we would not know that they were zombies.

If it is possible that zombies exist, then physicalism/materialism, the view that everything that exists is composed of physical matter, is false. If zombies are possible, then a being physically identical to a healthy conscious human being, but which lacks conscious experience, is possible. If such a being is possible, then consciousness is not fully determined by the physical. And if consciousness is not fully determined by the physical, then whatever accounts for consciousness is non-physical. Hence, physicalism is false.


Whether we give any attention to such a thought experiment depends on our individual intuitions - in my opinion, it seems quite plausible that a physical copy of myself could lack the conscious experiences that I have. But you might not agree.

Animal suffering

A cat suffering through a bad pun

A common argument for awarding animals moral rights is based on the notion of animal suffering. Since animals can suffer pain, some argue, they have moral rights. Thus we are morally obliged to prevent animal suffering. This conclusion is often directed at supporting the animal rights movement, and opposing the maltreatment of animals in the production of meat for human consumption, or animal testing.

Arguments such as this raise interesting questions surrounding how we view the relationship between humans and animals. Due to considerations surrounding human consciousness (see previous post - the Explanatory Gap), it might be tempting to place human beings in a fundamentally different category to animals, and use the fact that we are intellectually, morally and sociologically ‘transcendent’ as evidence for this. However, many supporters of the above argument (most notably Peter Singer) swing to the opposite extreme. On account of our common evolutionary origins, Singer argues, we are fundamentally just highly developed animals and nothing more. To discriminate against animals thus amounts to ‘species-ism’ - something analogous to racism. It is on these grounds that animals should be awarded moral 'rights'.

Perhaps Singer is right, and only through a misplaced sense of worth do we assume that we have transcended the evolutionary order. However, consider an unwelcome consequence of this reductive view. It would seem to follow that, since animals have moral rights on account of their ability to suffer, we have a duty to do all in our power to prevent animal suffering (apart from in extreme cases, where there are over-riding moral grounds not to do so). This would include actively intervening in nature to prevent one animal causing another animal to suffer. On this basis, we might accuse David Attenborough and his team of gross moral indecency for not intervening when sitting back and watching a lion hunting an antelope.

The advocate of animal rights cannot appeal to the old dictum ‘let nature run its course’ here to rule out this case, as on their view, human beings are as fundamentally part of the natural order as lions or antelopes. Since we have an obligation to prevent animal suffering, why not intervene? The case is especially forceful if one argues that, on the whole, there is more suffering overall in the (non-human) animal kingdom than good.

I (and I’m sure many others) don’t agree that we are morally obliged to intervene to save antelopes from lions - it’s a bizarre and impractical thing to suggest. But since we would ordinarily feel morally obliged to help a suffering human in need, and given Singer’s view that there is no fundamental moral difference between humans and animals, where and how can we draw the line?
  

The barber paradox

Paradoxes seen in 'Portal' as a means of confusing logic-based systems.

In a particular imaginary town, it is a policy that all men must be shaven. There are only two options available to each man - either the man must shave himself, or he must visit the barber to be shaven. There is only one barber in town, and his business is predictably doing well.

However, consider the barber. Who shaves him?

Perhaps the barber shaves himself. If a man shaves himself, then he must not be shaven by the barber - but the barber cannot help be shaven by the barber if he shaves himself, since he is the barber. Conversely, perhaps the barber is shaven by the barber instead. If a man is shaven by the barber, he must not shave himself - but in this case the barber does shave himself, since he is the barber. We are left with a paradox, since neither alternative is possible.

This is a classic exposition of the well-known ‘Russell’s Paradox.’ Trivial answers can be given in the context of the story, such as ‘the barber is a woman, and doesn’t need to shave’ or ‘the rules don’t apply to him, as he doesn’t live in the town.’ However, this is to miss the point of the story. Assume what is implied in the story - that the barber needs to shave at some point, and that he is a man who lives in the town, and abides by its rules. The paradox takes a plausible scenario, and shows it to be logically impossible.

Paradoxes of this sort arise due to the inclusion of what is called ‘self-reference’. Self-reference is present in the story because the barber is part of the rules governing all the men in the town, yet he himself is one of the men, and thus must abide by those rules too. Other paradoxes demonstrate the self-reference problem too - the elegant and simple claim, ‘this sentence is false.’ If it’s true, then it’s false, and if it’s false, then it’s true. (The Liar paradox).

Time travel and the grandfather paradox

Marty's mother would have married his father even without Marty's
heroic efforts to make sure it that it happened.

Is time travel the stuff of legend? Actually (and rather pleasingly), contemporary philosophers take the possibility much more seriously than you might think. Since it is generally considered that modern physics doesn’t conclusively rule out the possibility of time travel, room has opened up for philosophical speculation about what the possibility of time travel would mean for us as human beings. If time travel is possible after all, much of what we ordinarily assume about free will, causation, and time itself will turn out to be false.

Could you go back in time and, if you were so inclined, kill your own grandfather? Let’s assume that time travel is possible - that a human being could, given the right circumstances and resources, ‘travel’ back in time to events in the past. Let’s further suppose that such a person, Dave, is on a particular mission to kill his grandfather. Dave travels back into the past, and arrives on a sunny day in central London. Dave sees a vaguely familiar figure walking down the street - it is his grandfather, as a young man. Dave pulls a gun out of his back pocket and crouches behind a post-box, waiting for the perfect moment to strike...

But wait. What happens if Dave successfully kills his grandfather? Remember that we are in the past, and that Dave’s grandfather has yet to have a child (Dave’s father), who is in turn yet to have Dave. If Dave is successful in his assassination attempt, then his grandfather (being dead) will never have Dave’s father, and thus Dave will never be born. But if Dave is never born, then Dave could never have returned from the future in the first place to kill his grandfather in the past! Something has gone wrong.

We must ask the following question: is it within Dave’s power, given that he can travel back in time, to kill his grandfather? The answer is both 'yes' and 'no'. Insofar as Dave has a motive, willingness, and adequate resources (the gun, etc) to carry out the murder, he is able to kill his grandfather. However, in the grander scheme of things, Dave’s very existence in the future guarantees that he will not, in fact, succeed in his task. Crouching behind his post-box, Dave will suddenly have a change of heart. Or he will be grabbed by a passing policeman. Or he’ll be knocked over by a cyclist, allowing his grandfather time to escape. The specifics of the event that prevents Dave from firing the killer shot aren’t important - what is important is that whilst it is physically within Dave’s power to kill his grandfather in the past, it is logically impossible that he succeeds.

Philosophical reflection tells us that we should not try to kill our grandfathers. But then, we all knew that anyway.

(This puzzle is from David Lewis, The Paradoxes of Time Travel). 

Philosophers have beards

A couple of the 4th Century BC's greatest philosophers:

Plato

Aristotle

A couple of the 20th Century AD's greatest philosophers:

Lewis

Kripke

Ideas may advance, but beards remain in vogue.

The Explanatory Gap

Does contemplation of the Explanatory Gap suggest a God-given soul?

What is a mind? Are minds physical, or are they made out of a separate mental substance, a ‘soul’? Perhaps the way we live and the way we use language assumes the second option - that we have souls inside our heads, and that somehow, ‘I’ is a special subject, distinct from ‘my brain.’ In fact the mere phrase ‘my brain’ seems to imply that there are two things here - a brain and an owner, the person ‘within’ the brain. Thinking like this seems to fit well with everyday experience, and how we take ourselves to interact with the world. At least on the every-day level, we are dualists. 

The idea, however, that souls (perhaps God-given, if we are religious) reside within our bodies seems a little archaic on reflection. Science has taught us that a mind, at least in the context of our world, must be ‘physically realized‘ - it must arise out of physical matter. The question then arises as to how this could possibly happen. The physicalist has a quick answer - a mind just is the physical state of a brain. On this view, there is nothing else to conscious experience other than particular combinations of physical brain states.  

Physicalism is popular, and has been thrust towards the spotlight particularly recently outside philosophy, in the work of Richard Dawkins, who seems to assume that physicalism is so obviously true that we needn’t even bother debate about it. But this is too hasty - there are real questions to be raised about the nature of minds that physicalism cannot seem to account for. How can a subject possibly be in some way identical to physical matter? No matter how complex we make a physical organism, a strong intuition remains that we will never reach subjectivity - that rich ‘first person-ness‘ of human experience that perhaps is unique only to humans.

The religious are able to exploit this intuition and use it as a basis for positing that there are God-given souls that reside within our bodies, and which explain our conscious, intellectual, moral and spiritual abilities. However, we don’t need to be religious to acknowledge that the so-called mind-body problem cannot be easily shelved just by asserting physicalism. Science seems to be a fundamentally objective, third-person pursuit, and perhaps third-person facts are all that it will ever be able to explain. If this is the case, then consciousness, that mysterious first-person entity with which we as persons are identical, remains unexplained. There is an 'explanatory gap' between mind and matter.

(see further - the so-called ‘Explanatory Gap.’ http://en.wikipedia.org/wiki/Explanatory_gap)

Brains in vats

'Do you know? But do you REALLY know?'

Descartes invites us to imagine a scenario where everything we have ever experienced, and continue to experience, is a simulation, controlled by an evil demon with an aim solely to deceive us. More recently, philosophers have spoken of ‘brains in vats’ - imagine that we are actually brains floating in vats, in the lab of an evil scientist who is feeding us thoughts and experiences.

Both these possibilities entail that the external world (i.e. what we generally take to be the world around us) is not real, and that our entire perspective on life is in fact a delusion. I say ‘possibilities’ because, though it may seem unlikely, there is nothing in our experience that shows these scenarios to be false. If we were all were brains in vats, then our world would look no different to how it would if we really existed in the real physical world.

We may scoff at the thought of taking seriously these possibilities, and this is an understandable response - after all, let’s be honest, we’re probably not actually brains in vats. But the fact that such a scenario is possible raises famous and much-repeated philosophical problems about knowledge, and our ability to know what really is the case. If I asked you, ‘do you know that the world around you is real?’, then you would undoubtedly reply ‘yes, of course.’ However, it seems plausible that in order to really know that the world is real, we must first rule out the possibility that we are actually brains-in-vats. And since, goes the argument, we have no way of ruling this possibility out for definite, we have no way of knowing that the world around us is real! The fact that the possibility seems unlikely is not enough to conclusively rule it out.

The so-called ‘problem of scepticism’ is a problem about knowledge of the world, not the existence of the world itself. There is probably no mad scientist. Let’s take for granted that the world is most likely real - this is uncontroversial. However, even if we do this, the fact that we cannot properly rule out the possibility that we are brains-in-vats seems to threaten our knowledge of the world. We WANT to claim that we know the things we generally take ourselves to know...but, the problem of scepticism suggests that we cannot claim this. And so, our knowledge of everything falls away.