Author: Bill Vallicella

Still Trying to Understand Van Inwagen’s Half-Way Fregeanism about Existence

In section 53 of The Foundations of Arithmetic, Gottlob Frege famously maintains that

. . . existence is analogous to number.  Affirmation of existence is in fact nothing but denial of the number nought.  Because existence is a property of concepts the ontological argument for the existence of God breaks down. (65)

Frege is here advancing a double-barreled thesis that splits into two subtheses.

ST1. Existence is analogous to number.

ST2. Existence is a property (Eigenschaft) of concepts and not of objects.

In the background is the sharp distinction between property (Eigenschaft) and mark (Merkmal).  Three-sided is a mark of the concept triangle, but not a property of this concept; being instantiated is a property of this concept but not a mark of it.  The Cartesian-Kantian ontological argument "from mere concepts" (aus lauter Begriffen), according to Frege, runs aground because existence cannot be a mark of any concept, but only a property of some concepts.  And so one cannot validly argue from the concept of God to the existence of God.

Existence as a property of concepts is the property of being-instantiated.  We can therefore call the Fregean account of existence an instantiation account.

My concern in this entry is the logical relation between the subtheses.  Does the first entail the second or are they logically independent?  There is a clear sense in which (ST1) is true.  Necessarily, if horses exist, then the number of horses is not zero, and vice versa.  'So 'Horses exist' is logically equivalent to 'The number of horses is not zero.'  This is wholly unproblematic for those of us who agree that there are no Meinongian nonexistent objects.  But note that, in general, equivalences, even logical equivalences, do not sanction reductions or identifications.  So it remains an open question whether one can take the further step of reducing existence to instantiation, or identifying existence with instantiation, or even eliminating existence in favor of instantiation. 

(ST1), then, is unproblematically true if understood as expressing the following logical equivalence: 'Necessarily Fs exist iff the number of Fs is not zero.'  My question is whether (ST1) entails (ST2).  Peter van Inwagen in effect denies the entailment by denying that the 'the number of . . . is not zero' is a predicate of concepts:

I would say that, on a given occasion of its use, it predicates of certain things that they number more than zero.  Thus, if one says, 'The number of horses is not zero,' one predicates of horses that they number more than zero.  'The number of . . . is not zero' is thus what some philosophers have called a 'variably polyadic' predicate.  But so are many predicates that can hardly be regarded as predicates of concepts.  The predicates 'are ungulates' and 'have an interesting evolutionary history,' for example, are variably polyadic predicates.  When one says, 'Horses are ungulates' or 'Horses have an interesting evolutionary history' one is obviously making a statement about horses and not about the concept horse.  ("Being, Existence, and Ontological Commitment," pp. 483-484)

It is this passage that I am having a hard time understanding.   It is of course clear what van Inwagen is trying to show, namely, that the Fregean subtheses are logically independent and that one can affirm the first without being committed to the second.  One can hold that existence is denial of the number zero without  holding that existence is a property of concepts.

But I am having trouble with the claim that the predicate 'the number of . . . is not zero' is  'variably polyadic' and the examples van Inwagen employs.  'Robbed a bank together' is an example of a variably polyadic predicate.  It is polyadic because it expresses a relation and it is variably polyadic because it expresses a family of relations having different numbers of arguments.  For example, Bonnie and Clyde robbed a bank together, but so did Ma Barker and her two boys, Patti Hearst and three members of the ill-starred Symbionese Liberation Army, and so on.  (Example from Chris Swoyer and Francesco Orilia.) 

Now when I say that the number of horses is not zero, what am I talking about? It is plausible to say that I am talking about horses, not about the concept horse.  What I don't understand is why van Inwagen says that 'the number of . . . is not zero' is a variably polyadic predicate. As far as I can see, it is not even polyadic, let alone variably polyadic.  What is the relation that the predicate expresses, and why is that relation multigrade?  I grant that there are indefinitely many ways the number of horses could be not zero: there could be one horse, two, three, and so on.  But what is the relation between or among horses that this supposedly polyadic predicate expresses? 

'. . .exist(s)' is monadic.  It expresses no relation.  Why not say the same about 'such that their number is not zero'?

Now consider 'are ungulates.'  If an ungulate is just a mammal with hooves, then I fail to see how 'are ungulates' is polyadic, let alone variably polyadic.  'Are hooved mammals' is monadic.

The other example is 'Horses have an interesting evolutionary history.'  This sentence is clearly not about the concept horse. But it is not about any individual horse either.  Consider Harry the horse.  Harry has a history.  He was born in a certain place, grew up, was bought and sold, etc. and then died at a certain age.  He went through all sorts of changes.  But Harry didn't evolve, and so he had no evolutionary history.  No individual evolves; populations evolve:

Evolutionary change is based on changes in the genetic makeup of populations over time. Populations, not individual organisms, evolve. Changes in an individual over the course of its lifetime may be developmental (e.g., a male bird growing more colorful plumage as it reaches sexual maturity) or may be caused by how the environment affects an organism (e.g., a bird losing feathers because it is infected with many parasites); however, these shifts are not caused by changes in its genes.
While it would be handy if there were a way for environmental changes to cause
adaptive changes in our genes — who wouldn't want a gene for malaria resistance
to come along with a vacation to Mozambique? — evolution just doesn't work that
way. New gene variants (i.e., alleles) are produced by random mutation, and over the course of many generations, natural selection may favor advantageous variants, causing them to become more common in the population.

'Horses have an interesting evolutionary history,' then, is not about the concept horse or about any individual horse.  The predicate in this sentence appears to be non-distributive or collective.  It is like the predicate in 'Horses have been domesticated for millenia.'  That is certainly not about the concept horse.  No concept can be ridden or made to carry a load.  But it is also not about any individual horse.  Not even the Methuselah of horses, whoever he might be, has been around for millenia.

A predicate F is distributive just in case it is analytic that whenever some things are F, then each is F.  Thus a distributive predicate is one the very meaning of which dictates that if it applies to some things, then it applies to each of them.  'Blue' is an example.  If some things are blue, then each of them is blue.

If a predicate is not distributive, then it is non-distributive (collective).  If some Occupy-X nimrods have the building surrounded, it does not follow that each such nimrod has the building surrounded.  If some students moved a grand piano into my living room, it does not follow that each student did.  If bald eagles are becoming extinct, it does not follow that each bald eagle is becoming extinct.  Individual animals die, but no individual animal ever becomes extinct. If the students come from many different countries, it does not follow that each comes from many different countries.  If horses have an interesting evolutionary history, it does not follow that each horse has an interesting evolutionary history.

My problem is that I don't understand why van Inwagen gives the 'Horses have an interesting evlutionary history' example when he is committed to saying that each horse exists.  His view , I take it, is that 'exist(s)' is a first-level non-distributive predicate.  'Has an interesting evolutionary history,' however, is a first-level non-distributive predicate.  Or is it PvI's view that 'exist(s)' is a first-level non-distributive predicate?

Either I don't understand van Inwagen's position due to some defect in me, or it is incoherent.  I incline toward the latter.  He is trying to show that (ST1) doe not entail (ST2).  He does this by giving examples of predicates that are first-level, i.e., apply to objects, but are variably polyadic as he claims 'the number of . . . is not zero' is variably polyadic.  But the only clear example he gives is a predicate that is non-distributive, namely 'has an interesting evilutionary history.'  'Horses exist,' however, cannot be non-distributive.  If some horses exist, then each of them exists.  And if each of them exists, then 'exists' is monadic, not polyadic, let alone variably polyadic.

The ComBox is open if there is anyone who knows this subject and has read PvI's paper and can set me straight. 

Obama Lied Last Night About Arizona Senate Bill 1070

Here is the video clip of Obama lying to Romney and the rest of us in their second debate.  Obama lies when he claims that on the Arizona law (S. B. 1070) law enforcement  officers can stop people whom they merely suspect of being undocumented workers. Obama has told this lie before. 

The details are in an earlier post which I now reproduce:

Debra Saunders' article begins:

President Barack Obama hailed the Supreme Court's 5-3 decision Monday that struck down most of Arizona's 2010 immigration law. In a statement released by the White House, however, the president said that he remains "concerned about the practical impact of the remaining provision of the Arizona law that requires local law enforcement officials to check the immigration status of anyone they even suspect to be here illegally."

All eight voting members of the Supreme Court upheld this provision, which requires
that Arizona cops try to determine the immigration status of individuals who have been stopped for reasons not involving immigration.

Please note the difference between what the president is quoted as saying and what Saunders correctly reports the S.B. 1070 provision as requiring.  The law requires "that Arizona cops try to determine the immigration status of individuals who have been stopped for reasons not involving immigration." President Obama of course knows this.  So Obama lied in his statement when he said that "the Arizona law that requires local law enforcement officials to check the immigration status of anyone they even suspect to be here illegally."

Obama's egregious misrepresentation has been repeated time and again by leftists over the last two years.  See my 1 June 2010 post, The Misrepresentations of Arizona S. B. 1070 Continue.  Other
of my 1070 posts are to be found in the Arizona category.

Why are leftists so mendacious?  Because in their scheme the glorious end justifies the scurrilous means.

Don't forget to read the rest of Saunders' article.

Why Keep a Journal?

It was 42 years ago today that I first began keeping a regular journal. Before that, as a teenager, I kept some irregular journals. Why maintain a journal? When I was 16 years old, my thought was that I
didn't want time to pass with nothing to show for it. That is still my thought. The unrecorded life is not worth living. For we have it on good authority that the unexamined life is not worth living, and how examined could an undocumented life be?


The maintenance of a journal aids mightily in the project of self-individuation. Like that prodigious journal writer Søren Kierkegaard, I believe we are here to become actually the individuals we are potentially. Our individuation is not ready-made or given, but a task to be accomplished. The world is a vale of soul-making; we are not here to improve it, but to be improved by it. 


Thoreau journalHenry David Thoreau, another of the world's great journal writers,  said in Walden that "Most men live lives of quiet desperation." I  would only add that without a journal, one's life is one of quiet dissipation. One's life dribbles away, day by day, unreflected on, unexamined, unrecorded, and thus fundamentally unlived. Living, for us, is not just a biological process; it is fundamentally a spiritual unfolding. To mean anything it has to add up to something, and that something cannot be expressed with a dollar sign.

I have always had a horror of an unfocused existence. In my early twenties, I spoke of the supreme desideratum of a focused existence.  What bothered me about the people around me, fellow students in particular, was the mere aestheticism of their existence: their aimless drifting hither and yon, their lack of commitment, their unseriousness, their refusal to engage the arduous task of   self-definition and self-individuation, their willingness to be guided and mis-guided by social suggestions. In one's journal one collects and re-collects oneself; one makes war against the lower self and the
forces of dispersion.

Another advantage to a journal and its regular maintenance is that one thereby learns how to write, and how to think. An unwritten thought is still a half-baked thought: proper concretion is achieved only by  expressing thoughts in writing and developing them. Always write as well as you can, in complete sentences free of grammatical and spelling errors. Develop the sentences into paragraphs, and if the  Muse is with you those paragraphs may one day issue in essays, articles, and chapters of books.

Finally, there is the pleasure of re-reading from a substantial temporal distance.  Two years ago I began re-reading my journal in order, month by month, at a 40 year distance.  So of course  now I am up to October 1972.  40 Years from now I will be at the present, or dead. One.

Ron Radosh on the Woody Guthrie Tribute Concert

Good music, dreadful politics.  Excerpt:

Unfortunately, the entire event was marred by the hard Left narrative particularly voiced in the most offensive manner by two artists, Tom Morello and Ry Cooder. At least Cooder is a real musician, but that does not excuse his behavior and his leftist rants delivered both in asides and in the rewriting of Guthrie’s lyrics. Cooder sang a little known Guthrie song written towards the end of WW II about how the fascists would all lose. Cooder commented, to great applause from the leftist audience, that we won that fight, but the fascists were still here, and he knew they would be defeated on election day. Singing Guthrie’s “Vigilante Man,” about hired thugs of the coal companies in the early 20th Century, Cooder changed a lyric to make it about the Trayvon Martin case.  He could have grown up to be President, he said, “but he was killed by a vigilante man.” Then he sang a new verse about how those in the audience should not tell anyone that they attended the concert, or they too might be killed!

Does Ry Cooder really believe that paying an average of $100 for a Kennedy Center concert could lead anyone to be harmed, not to say murdered? Doesn’t he know that by now, Woody Guthrie is a celebrated national hero, honored and revered by many, and no kind of danger to anyone who sings his songs?

How Cooder could be such an idiot is beyond me, but then he is not atypical.  Artists, actors, and musicians hang with their own left-leaning ilk and are never exposed to conservative or libertarian points of view.  They reinforce each others' prejudices.  Denouncing bigotry in others, they exemplify it in excelsis.  Masters of psychological projection, they cannot face what they project into others.  They can emote in all sorts of creative ways, but they cannot think.

Play Ry, play.  But shut up about politics until you learn something.  Two favorites of mine: Yellow Roses. He'll Have to Go.

Radosh reports that Arlo Guthrie is a registered Republican and libertarian.  At least he has his head screwed on Right.  City of New Orleans.  A great piece of Americana.

Can Reason Be Understood Naturalistically? More Notes on Nagel

This is the third in a series of posts on Thomas Nagel's Mind and Cosmos (Oxford 2012).  The first is an overview, and the second addresses Nagel's reason for rejecting theism.  This post will comment on some of the content in Chapter 4, "Cognition."

In Chapter 4,  Nagel tackles the topic of reason, both theoretical and practical.  The emphasis is on theoretical reason, with practical reason receiving a closer treatment in the following chapter entitled "Value."

We have already seen that consciousness presents a problem for evolutionary reductionism due to its irreducibly subjective character.  (For some explanation of this irreducibly subjective character, see my Like, What Does It Mean?)

'Consciousness' taken narrowly refers to phenomenal consciousness, pleasures, pains, emotions, and the like, but taken widely it embraces also thought, reasoning and evaluation.  Sensory qualia are  present in nonhuman animals, but only we think, reason, and evaluate.  We evaluate our thoughts as either true or false, our reasonings as either valid or invalid, and our actions as either right or wrong, good or bad.  These higher-level capacities can be possessed only by beings that are also conscious in the narrow sense.  Thus no computer literally thinks or reasons or evaluates the quality of its reasoning imposing norms on itself as to how it ought to reason if it is to arrive at truth; at best computers simulate these activities.  Talk of computers thinking is metaphorical.  This is a contested point, of course.  But if mind is a biological phenomenon as Nagel  maintains, then this is not particularly surprising.

What makes consciousness fascinating is that while it is irreducibly subjective, it is also, in its higher manifestations, transcensive of subjectivity. (This is my formulation, not Nagel's.)  Mind is not trapped within its interiority but transcends it toward impersonal objectivity, the "view from nowhere."  Consciousness develops into "an instrument of transcendence that can grasp objective reality and objective value." (85)  Both sides of mind, the subjective and the objective, pose a problem for reductive naturalism.  "It is not merely the subjectivity of thought but its capacity to transcend subjectivity and to dsiscover what is objectively the case that presents a problem." (72)

Exactly right!  One cannot prise apart the two sides of mind, segregating the qualia problem from the intentionality problem, calling the former 'hard' and imagining the latter to be solved by some functionalist analysis.  It just won't work.  The so-called Hard Problem is actually insoluble on reductive naturalism, and so is the intentionality problem.  (Some who appreciate this go eliminativist — which is a bit like getting rid of a headache by blowing one's brains out.)

The main problem Nagel deals with in this chapter concerns the reliability of reason.  Now it is a given that reason is reliable, though not infallible, and that it is a source of objective knowledge.  The problem is not whether reason is reliable as a source of knowledge, but how it it is possible for reason to be reliable if  evolutionary naturalism is true.  I think it is helpful to divide this question into two:

Q1. How can reason be reliable if materialist evolutionary naturalism is true?

Q2. How can reason be reliable if evolutionary naturalism is true?

Let us not forget that Nagel himself is an evolutionary naturalist.  He is clearly  a naturalist as I explained in my first post, and  he does not deny the central tenets of the theory of evolution.  His objections are to reductive materialism (psychophysical reductionism) and not to either naturalism or evolution. Now Nagel is quite convinced, and I am too, that the answer to (Q1) is that it is not possible for reason to be relied upon in the manner in which we do in fact rely upon it, if materialism is true.  The open question for Nagel is (Q2).  Reason is reliable, and some version of evolutionary naturalism is also true.  The problem is to understand how it is possible for both of them to be true.

Now in this post I am not concerned with Nagel's tentative and admttedly speculative  answer to (Q2).  I hope to take that up in a subsequent post.  My task at present is to understand why Nagel thinks that it is not possible for reason to be reliable if materialism is true.

Suppose we contrast seeing a tree with grasping a truth by reason. 

Vision is for the most part reliable:  I am, for the most part, justified in believing the evidence of my senses.  And this despite the fact that from time to time I fall victim to perceptual illusions.  My justification is in no way undermined if I think of myself and my visual system as a product of Darwinian natural selection.  "I am nevertheless justified in believing the evidence of my senses for the most part, because this is consistent with the hypothesis that an accurate representation of the world around me results from senses shaped by evolution to serve that function." (80)

Now suppose I grasp a truth by reason. (E.g., that I must be driving North because the rising sun is on my right.)  Can the correctness of this logical inference be confirmed by  the reflection that the reliability of logical thinking is consistent with the hypothesis that evolution has selected instances of such thinking for accuracy?

No, says Nagel and for a very powerful reason.  When I reason I engage in such operations as the following: I make judgments about consistency and inconsistency; draw conclusions from premises; subsume particulars under universals, etc.  So if I judge that the reliability of reason is consistent with an evolutionary explanation of its origin, I presuppose the reliability of reason in making this very judgement.  Nagel writes:

It is not possible to think, "reliance on my reason, including my reliance on this very judgment, is reasonable because it is consistent with its having an evolutionary explanation." Therefore any evolutionary account  of the place of reason presupposes reason's validity and cannot confirm it without circularity. (80-81)

Nagel's point is that the validity of reason can neither be confirmed nor undermined by any evolutionary account of its origins.  Moreover, if reason has a merely materialist origin it would not be reliable, for then its appearance would be a fluke or accident.  And yet reason is tied to organisms just as consciousness is.  Nagel faces the problem of explaining how reason can be what it is, an "instrument of transcendence" (85) and a "final court of appeal" (83), while also being wholly natural and a product of evolution.  I'll address this topic in a later post. 

Why can't reason be a cosmic accident, a fluke?  This is discussed in my second post linked to above, though I suspect I will be coming back to it.

Roger Scruton on the Art of the Aphorism

Speaking Neatly. Excerpt:

FALSE APHORISMS are not as rare as one might think. More significant than Wilde's, on account of its influence, is Marx's dismissal of religion as "the opium of the people." For this implies that religion is adopted purely for its ability to soothe the wounds of society, and that there is some other condition to which humanity might advance in which religion would no longer be needed. Both those implications are false, but they are boiled into a stock cube as tasty as any that has been seen on the intellectual menu. How many would-be intellectuals have dissolved this cube into their prose and given their thought, in the manner of Christopher Hitchens, a specious air of wisdom?

Permit me a quibble.  Should we call a striking formulation lifted from a wider context an aphorism?  I don't think so.  An aphorism by my lights is a pithy observation intended by its author to stand alone.  Accordingly, Marx's famous remark is not an aphorism.  The wider context is provided here.

Dylan’s New Album

In lieu of oldies this Saturday night, a taste of  Bob Dylan's latest, Tempest.  Duquesne Whistle.  Sampler. 1962 version of "Roll on, John"  50 years of  assimilation  and creative  reworking of musical Americana by the unlikely Jewish kid from Hibbing, Minnesota.

Jody Rosen's New Yorker review. Insightful:

The hunt for Dylan in Dylan songs is a mug’s game. Dylan is a genius; he’s also  the greatest bullshitter and jive-talker in popular-music history. He began  laying boobytraps for his exegetes before he even had any, and they—we—have  never stopped taking the bait. Today Dylanology is a midrashic enterprise  rivaling Talmudism and Shakespeare Studies, and it’s worth remembering its  origins: it started with the hippie gadfly A .J. Weberman, who took to “reading” toothbrushes recovered from garbage bins outside of Dylan’s MacDougal Street  townhouse.

[. . .]

The original Dylanological sin is to focus too much on the words, and too little  on the sound: to treat Dylan like he’s a poet, a writer of verse, when of course  he’s a musician—a songwriter and, supremely, a singer. “Tempest” reminds us what  a thrilling and eccentric vocalist he is.

Scientism

Those who hold that the only knowledge is scientific knowledge will not be content to restrict themselves to such knowledge; they will be tempted to pass off as scientific what is not.  The prime and best example is scientism itself: it is passed off as scientific when it is a philosophical thesis with all the rights, privileges, and debilities pertaining thereunto.

(Details in Scientism category.)

Why are People So Easy to Swindle?

People are so easy to swindle because the swindler has as accomplices the victim's own moral defects.  When good judgment and moral sense are suborned by lust or greed or sloth or vanity or anger, the one swindled participates willingly in his own undoing.  In the end he swindles himself.

How is it, for example, that Bernie Madoff 'made off' with so much loot?  You have  otherwise intelligent people who are lazy, greedy and vain: too lazy to do their own research and exercise due diligence, too greedy to be satisfied with the going rate of return, and too vain to think that anything bad can happen to such high-placed and sophisticated investors as themselves.

Or take the Enron employees.  They invested their 401 K money in the very firm that that paid their salaries!  Now how stupid is that?  But they weren't stupid; they stupified themselves by allowing the subornation of their good sense by their vices.

The older I get the more I appreciate that our problems, most of them and at bottom, are moral in nature.  Why, for example, are we and our government in dangerous debt?  A lack of money?  No, a lack of virtue.  People cannot curtail desire, defer gratification, be satisfied with what they have, control their lower natures, pursue truly choice-worthy ends.

Nagel’s Reason for Rejecting Theism

This is the second in a series.  My overview of Thomas Nagel's new book, Mind and Cosmos, is here.

I agree with Nagel that mind is not a cosmic accident.  Mind in all of its ramifications (sentience, intentionality, self-awareness, cognition, rationality, normativity in general) could not have arisen from mindless matter.  To put it very roughly, and in my own way, mind had to be there already and all along in one way or another.  Not an "add-on" as Nagel writes, but "a basic aspect of nature." (16) 

Two ways mind could have been there already and all along are Nagel's panpsychistic way and the theistic way.  My task in this entry is to understand and then evaluate Nagel's reasons for rejecting theism.  

But first let's back up a step and consider the connection between mind and intelligibility.  That the world is intelligible is a presupposition of all inquiry.  The quest for understanding rests on the assumption that the world is understandable, and indeed by us.  The most successful form of this quest is natural science.  The success of the scientific quest is evidence that the presupposition holds and is not merely a presupposition we make.  The scientific enterprise reveals to us an underlying intelligible order of things not open to perception alone, although of course the confirmation of scientific theories requires perception and the various instruments that extend it.

Now what explains this underlying rational order? Two possibilities.  One is that nothing does: it's a brute fact.  It just happens to be the case that the world is understandable by us, but it might not have been.  The rational order of things underpins every explanation but  itself has no explanation.  The other possibility is that the rational order has an explanation, in which case it has an explanation by something distinct from it, or else is self-explanatory.  On theism, the world's  rational order is grounded in the divine intellect and is therefore explained by God.  On what I take to be Nagel's view, the rational order is self-explanatory, a necessary feature of anything that could count as a cosmos.

Nagel views the intelligibility of the world as "itself part of the deepest explanation why things are as they are." (17).  Now part of the way things are is that they are understandable by us.  Given that the way things are is intelligible, it follows that the intelligibility of the world is self-explanatory or self-grounding.

"The intelligibility of the world is no accident." (17)  The same is true of mind.  The two go together: an intelligible world is one that is intelligible to mind, and mind is mind only if it can 'glom onto' an antecedent order of things.  (This is my way of putting it, not Nagel's!)  Intelligibility is necessarily mind-involving, and mind (apart from mere qualia) is necessarily an understanding of something.  One could say that there is an antecedent community of nature between mind and world which allows mind to have an object to understand and the world to be understandable by mind.  What I am calling the antecedent community of nature between mind and world Nagel expresses by saying that "nature is such as to give rise to conscious beings with minds; and it is such as to be comprehensible to such beings." (17)

That neither mind nor intelligibility are cosmic accidents, and that they 'go together' as just explained  could be accepted by both Nagelian panpsychists and theists.  So why does Nagel reject theism?

His main reason seems to be couched in the following quotations:

. . . the disadvantage of theism as an answer to the desire for comprehensive understanding is not that it offers no explanations but that it does not do so in the form of a comprehensive account of the natural order. [. . .] But it would not be the kind of understanding that explains how beings like us fit into the world.  The kind of intelligibility that would still be missing is intelligibility of the natural order itself — intelligibility from within. (25-26)

Nagel does not do a very good job of presenting his argument clearly, but the following is what I take him to be driving at.

Materialism cannot explain the origin of life from inanimate matter, the origin of consciousness from pre-conscious life, or the origin of reason in conscious beings.  Nondeistic theism can explain these crucial transitions by means of divine interventions into the workings of nature.  (Deism would leave the crucial transitions as brute facts and is  rejectable for this reason.)  To subscribe to such interventionist hypotheses, however, is to deny that there is a comprehensive natural order.  Nature would not be intelligible from within itself, in its own terms.  So maybe Nagel's argument could be put like this:

1. Nature is immanently intelligible: it has the source of its intelligibility entirely within itself and not from a source outside itself.

2. On theism, nature is not immanently intelligible: God is the source of nature's intelligibility. (This is because divine intervention is needed to explain the crucial transitions to life, to consciousness, and to reason, transitions which otherwise would be unintelligible.)

Therefore

3. Theism suffers from a serious defect that make it reasonable to pursue a third course, panpsychism, as a way to avoid both materialism and theism.

Now I've put the matter more clearly than Nagel does, but I'd be surprised if this is not what he is arguing, at least on pp 25-26.

As for evaluation, the argument as presented is reasonable but surely not compelling. A theist needn't be worried by it.  He could argue that it begs the question at the first premise. How divine interventions into the course of nature are so much as possible is of course a problem for theists, but Plantinga has an answer for that.  The theist can also go on the attack and mount a critique of panpsychism, a fit topic for future posts. 

There is also the question of why the cosmos exists at all.  It is plausible to maintain that the cosmos is necessarily intelligible, that it wouldn't be a cosmos if it weren't.  But necessary intelligibility is consistent with contingent existence.  Will Nagel say that the cosmos necessarily exists?  How would he ground that?  Panpsychism, if tenable, will relieve us of the dualisms of matter-life, life-consciousness, mind-body.  But it doesn't have the resources to explain the very existence of the cosmos.