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Seymour asked:

Who, in your opinion, is the most important philosopher of all time?

Answer by Craig Skinner

In my opinion, Aristotle.

To see why, read my article at:


Alex asked:

What is Descartes Methodological Doubt, and why does he insist/want to use it? What is the one “true” idea that is derived from this doubting? What is his proof for God (the trademark version ie the causal argument), and more importantly (ie specifically),what is the problem with it – why does his argument fail – please specify in detail this problem?

Answer by Craig Skinner

Descartes was tired of scholastic philosophy, viewing it as hairsplitting logic, nitpicking metaphysics,  postulated occult powers, preoccupation with theological matters such as transsubstantiation and the holy trinity, and acceptance of Aristotle’s creaky cosmology and physics. On the other hand, he was enthusiastic about the new “mechanical philosophy” (physics), and thought such empirically-based science, coupled with mathematics, might yield more understanding and also control of nature to our benefit.

So he wanted to start from scratch and “build anew from the foundations… to establish… firm and permanent structure in the sciences”.

He says that many of his former beliefs were false or doubtful. So a new foundation had to be a belief that can be relied on as absolutely certain. How to arrive at such a belief? The first Meditation spells this out – his famous method of doubt.

He says he will doubt everything that can conceivably be doubted. This includes all beliefs based on the senses and all beliefs based on reason.

As regards the senses, we can doubt them because

(a) they sometimes deceive us, a commonplace observation.

(b) when I dream I think I am awake and doing things. So, at any time when I think I am awake, I might really be dreaming, and all the assumed external world an illusion.

(c) a malicious demon could put ideas in my mind suggesting an external world when no such thing exists.

As regards reason, he feels that although we think we know, say, 2+3=5 with certainty, again a malicious demon could trick us so that every time we add these numbers we make a mistake, thinking the sum is 5 when it isnt.

He concludes that the heavens, earth, colours, figures, sounds, all external things including his own body may be illusory.

What then is left as his foundational belief, his “one true idea” as you put it?

He tells us this in the second Meditation. He says that if he is doing all this doubting, he must be thinking, and so must exist. “I think therefore I am” (“cogito ergo sum”), as it is famously worded elsewhere in his writings.

Of course by itself this doesnt get him far. The world might consist of just one thinking thing, himself. To guarantee the rest of the world he needs the existence of the guarantor, God, a non-deceiving God at that, to be another certainty. He cant have this of course. First, to say that his clear and distinct idea of God can be relied on because the idea was implanted by God, is to beg the question. Secondly, no proof of God’s existence is sound.

But he has a go. He seems to think that God’s existence is readily evident to any diligent meditator, and that arguments are just heuristic devices to help the slower meditator to the almost self-evident truth that God’s existence is known by clear and distinct perception. So he doesnt set out his arguments formally with premises and conclusion. Also he uses a lot of scholastic terms. We meditators have to work hard to penetrate his arguments.

You ask about the causal argument (Meditation 3)

A fair reconstruction is as follows:

P1. I have the idea of a most perfect (omnipotent, eternal, infinite, benevolent) being (God).

P2. A cause must be at least as great (real) as its effect.

Conclusion: the idea of God cant come from (imperfect) me. Its cause must be God (or, impossibly, greater). God exists.

The argument is valid. To declare it unsound we therefore need to attack the premises. Both are vulnerable to attack.

Objections to P1:

(a) a finite mind cant have an idea of infinity (Gassendi’s view in 5th Objections). Descartes replied that we can. It’s our understanding that’s limited, not the the thing of which we have (limited) understanding. I agree.

(b) the meditator can claim not to have this idea. Descartes assumes we all have the same (God-given) innate ideas. We simply dont need to accept this. I dont.

Objections to P2:

P2 isnt easy to grasp. The discussion is in technical, scholastic terms. Two types of reality (being) are distinguished regarding ideas. The existence of an idea (its formal reality) is distinguished from its content (its objective reality). “Objective” refers to the object contained in the idea, rather like the modern use of “subjective” – it refers to the tree (say) in the mind not the tree in the garden. The notion of degrees of reality is then introduced. Ideas all have the the same degree of formal reality, all being mind states, but they differ in degrees of objective reality – lowest in a mode (modification of a substance eg  colour), intermediate in a finite substance, highest in an infinite substance. P2 therefore expresses the Causal Principle that the degree of formal reality of the cause must be at least as great as the objective reality of the effect, leading to the conclusion that an idea whose content (objective reality) is infinite (such as Descartes’ idea of God) cant have its cause in a finite being (with less than infinite formal reality), such as me, only in God, so that God exists.

First objection: the idea of God can come from me – having some degree of perfection, I can posit higher and higher degrees indefinitely (Mersenne’s view in 2nd Objections). I agree.

Second objection: animals and plants (greater) derive from inanimate causes (lesser), Mersenne’s view in 2nd Objections. I agree.

Third objection: P2 is just an assertion. No evidence is given for it. I  would generalize Mersenne’s objection to say that simple things plus simple rules can lead to complex things eg laws of nature plus simple initial conditions in our universe has yielded, atoms, compounds, galaxies, life and minds, so that the Causal Principle is false. To assume that a finite mind needs an infinite mind to cause it begs the question as to God’s existence.

In short, the first premise can simply be denied, the second premise is false and question begging.

In the end, Descartes doesnt get further than the cogito, so that, far from establishing a new foundation, his philosophical legacies are the idea of scepticism, and, arising from his idea that I am essentially a thinking thing, the notion of mind -body dualism. Scepticism is a commonplace now in philosophy, science and everyday thinking – we all accept that certainty is only to be found in logic and mathematics. Dualism displaced Aristotle’s substance/form view, but has proved sterile, and the superiority of Aristotle’s view is increasingly recognized.


Frem asks:

What do you call ‘mental sanity’? Would anyone dare to answer?

Answer by Craig Skinner

Here’s an answer, although I dont feel daring.

“Sanity” means “health” (Latin sanus=healthy) so that “mental sanity” means “mental health”. However,the term is rarely used when speaking of physical health, so that “sanity”/”insanity” refer to mental health/disease (and some physical diseases eg syphilis, can also produce mental disease).

The notion of “insanity” is narrower than “mentally ill” Most mentally ill people are not insane. “Insanity” implies that the disease is bad enough to cause loss of reason, inability to tell right from wrong, and is a term used by lawyers rather than doctors these days, as “not guilty by reason of insanity” is a common defence to a murder charge. Among doctors and nurses, the terms “delirium” and “psychosis” are respectively used for fleeting and persistent loss of reason. Delirium can be due to feverish illness, drugs or alcohol, and psychosis is usually due to schizophrenia or severe bipolar disorder.

In short, sanity implies mental health, or mental illness insufficient to cause loss of reason. The term is often used loosely to express praise in other contexts (eg sane policies).

There is a tendency for lawyers to extend the insanity defence beyond the conditions I have mentioned, to include, for example, genetic variants known to be associated with aggression, or people with damage to the amygdala causing lack of emotional response to another’s suffering, the “my brain made me do it” defence. One difficulty for the defendant here is that if the defence be accepted, and nothing can be done to change the brain, he is liable to be locked up for at least as long as if he plead guilty.

I wonder if your mention of anyone “daring” to answer, reflects the view that there is no real sanity/insanity distinction, just labelling by the regime in power of their views and those expressed by opponents. It is true that some regimes have labelled troublesome “dissidents” insane and locked them up, and this still goes on. But this is abuse of psychiatry, and shameful activity by doctors involved. It doesnt mean that mental illness is an arbitrary social construct. Tell that to my sister with schizophrenia or my cousin with bipolar disorder whose lives were ruined by their illness, although greatly helped by medication and ECT.


Kenneth asked:

Does there exist a philosophical term for a general “Hate/ disgust for the contemporary society/ modern world”.  I think it’s becoming quite widespread. I would myself like to suggest: Pan-misanthropy.

Answer by Craig Skinner

You clearly dont have in mind, say,  the desperation of ordinary people in contemporary Syria, or those starving to death in poor countries.  Rather, an attitude of people in stable societies who can count on a roof over their heads, clean water  and enough to eat.

I dont think a negative view specifically of the modern world is specially common in philosophers.

Of course, since time immemorial, the older generation has thought the world is going to the dogs, morals are getting lax, respect for elders has gone, violence is on the rise, community spirit is gone etc. This is usually coupled with a rosy view of their young day when we all helped each other and had no need to lock our doors. The word that springs to mind here is “nostalgia”. The facts are against these oldies. All research shows the world to be a safer, more healthy place now than it ever was. If the level of violence, robbery and murder in Oxford was what it was in medieval times or in a typical stone-age society, I’d be frightened to go there for a pub lunch. Never mind disease, early death, oppression and lack of civil liberty in the good old days.

Among philosophers, despair is sometimes expressed, not about the modern world, but about the perennial human condition. Bertrand Russell, reflecting on the vast, empty, purposeless universe and future extinction of the solar system revealed by science, famously said in 1903:

“Only on the firm foundation of unyielding despair, can the soul’s habitation henceforth be safely built.” (‘A Free Man’s Worship’)

Despite this he went on to live a very long enjoyable, productive and interesting life.

Another famously pessimistic philosopher who enjoyed a long and comfortable life was Schopenhauer.

And then we have the existentialists expressing “angst” and “ennui” about the human condition, usually while drinking coffee in upmarket cafes or debating in nicely-furnished drawing rooms.

Existentialist joke:

Scene: family car en route to holiday destination.

Small boy: Dad, Dad! I feel ennui.

Father: Well, I’m not stopping. You should have reconciled yourself to the absurdity of life before we got into the car.

Dont trust philosophers bearing despair. Dont join the panmisanthropists, as you term them. If you feel it coming on, think again. You can make a difference.


Joseph Kirby asked:

How can evolution explain that birds with such amazing colorful feathers were developed?

Answer by Craig Skinner

Traits evolve in a breeding population if they are adaptive. A heritable trait, randomly arising in an individual, will spread if it improves the chances of the individual surviving or reproducing. In short, natural selection of favorable variations.

But how can bright plumage be favorable? At first sight it seems maladaptive, making the bird easier for predators to spot.

The answer, in general, is that female birds find bright plumage attractive so that bright males have a reproductive advantage and leave more offspring.

This is an example of sexual selection (described in detail by Darwin) where traits arise in one sex (usually males) which are either attractive to females (as with bright bird plumage) or help males to compete for females (as with antlers in deer).

Sometimes, there are other explanations for bright plumage. Field work has shown that some birds benefit, not because of female preference, but because the plumage signals to competitors that a territory is occupied. And in yet other cases, the chemistry that makes the plumage bright makes the flesh taste bad, and predators learn to avoid these birds and concentrate on drabber birds.

Finally, bird eyes have four types of cone as compared with three in humans. Hence birds have much fuller colour vision than us. In particular they can see in the ultraviolet part of the spectrum which is invisible to us, so that birds whose plumage looks dull grey or brown to us may be seen by other birds in gorgeous colours that we cant even imagine.

This is an active research field and there is much more to be said about bird plumage both in males and in females. But explanation is on standard, modern evolutionary lines (natural and sexual selection, genetics and epigenetics).


Bob asked:

There is a tenet still held by some philosophers which is: “Anything that can be imagined is possible”. This was, of course, the basis of Anselm’s ontological argument. My question: What is the formal name of that tenet?

Answer by Craig Skinner

This is called the conceivability argument.

Such arguments are advanced against physicalism, the doctrine that the physical world is all that exists, and that mental states are just physical brain states or aspects of these.

The two best known conceivability arguments are the inverted spectrum argument and the zombie argument.

The inverted spectrum argument says that, for all we know, the sensations you have when looking at colours are the inverse of mine. So, looking at grass, you have the sensation I have when looking at ripe tomatoes, and, looking at ripe tomatoes, you have the sensation I have looking at grass. Of course we both call grass green and tomatoes red, having been so taught, so that there is no communication problem. The argument assumes healthy humans, not people with colour blindness or jaundice.

The zombie argument says that we can conceive of an atom-for-atom duplicate of you, with exactly the same brain states as you, behaving exactly as you, but without any consciousness at all.

So, we can conceive brain states occurring with a mental accompaniment different from usual, or with no mental state at all.. Hence (goes the conceivability argument), whatever causes mental states, they are not wholly determined by brain states, hence physicalism is false.

I think these are poor arguments. I have two objections.

First, conceivability doesnt necessarily mean possibility. Our imagination can outrun possibility. So, the “tenet”, as you term it, is false. Right now, I can conceive my cat jumping up and typing the rest of this answer. But this is metaphysically impossible. There could of course be worlds in which cat-like creatures with superior intelligence do such things, but they would not be cats.

Secondly, advances in our understanding may show that the arguments contain conceptual confusions. Two conceivability arguments that might have been advanced in the 19th Century illustrate this:

  1. We can conceive of a container of gas in which the particles move faster and faster but the temperature of the gas doesnt rise. So, whatever temperature is, it’s nothing to do with particle velocity, right? Wrong, temperature just IS mean particle velocity.
  2. We can conceive of a world containing tiny, replicating, self-stabilizing bags of chemicals undergoing complex interactions (let’s call them ‘cells’) but these cells are not alive, just little bags of dead chemicals. So, whatever life is, it’s not explained by complex chemical interactions. Again, wrong. Life just IS complex interactions of dead chemicals in units drawing energy from outside, maintaining dynamic stability and replicating.

So, I think the spectrum and zombie arguments may likewise fall to advances in cognitive science as we learn how particular brainstates necessarily entail, say, seeing red or being conscious. Meantime, I would say these arguments imagine things that are not possible.



Books by Geoffrey Klempner

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