Arthur C Clarke

Arthur C. Clarke is best remembered for this science fiction stories, but many of his dicta and aphorisms have become common currency and are quoted and repeated to the point that their connection to their source is sometimes lost. (Clarke’s thought ranged widely and, interestingly, Clarke identified himself as a logical positivist.) Recently I quoted one of Clarke’s well-known sayings in Happy Birthday Nicolaus Copernicus!, as follows:

“Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.”

quoted in Visions: How Science Will Revolutionize the Twenty-First Century (1999) by Michio Kaku, p. 295

In so saying, Clarke asserted a particular case of what is known as the logical law (or principle) of the excluded middle, which is also known as tertium non datur: the idea that, given a proposition and its negation, either one or the other of them must be true. This is also expressed in propositional logic as “P or not-P” (“P v ~P”). The principle of tertium non datur is not to be confused with the principle of non-contradiction, which can be formulated as “~(P & ~P).”

Even stating tertium non datur is controversial, because there are narrowly logical formulations as well as ontological formulations of potentially much greater breadth. This, of course, is what makes the principle fascinating and gives it its philosophical depth. Moreover, the principle of the excluded middle is subtly distinct from the principle of bivalence, though the two usually work in conjunction. Whereas the law of the excluded middle states that of a proposition and its negation, one of the other must be true, the principle of bivalence states that there are only two propositional truth values: true and false.

To get started, here is the principle of the excluded middle as formulated in The Cambridge Dictionary of Philosophy edited by Robert Audi:

principle of excluded middle, the principle that the disjunction of any (significant) statement with its negation is always true; e.g., ‘Either there is a tree over 500 feet tall or it is not the case that there is such a tree’. The principle is often confused with the principle of bivalence.

THE CAMBRIDGE DICTIONARY OF PHILOSOPHY second edition, General Editor Robert Audi, 1999, p. 738

And to continue the Oxbridge axis, here is the formulation from Simon Blackburn’s The Oxford Dictionary of Philosophy:

excluded middle, principle (or law) of The logical law asserting that either p or not-p. It excludes middle cases such as propositions being half correct or more or less right. The principle directly asserting that each proposition is either true or false is properly called the law of bivalence.

The Oxford Dictionary of Philosophy, Simon Blackburn, Oxford University Press, 1996, p. 129

For more partisan formulations, we turn to other sources. Mario Bunge formulated a narrowly syntactical conception of the law of the excluded middle in his Dictionary of Philosophy, which is intended to embody a scientistic approach to philosophy:

EXCLUDED MIDDLE A logical truth or tautology in ordinary (classical) logic: For every proposition p, p v ~p.

Dictionary of Philosophy, Mario Bunge, Prometheus Books, 1999, p. 89

By way of contrast, in D. Q. McInerny’s Being Logical: A Guide to Good Thinking we find a strikingly ontological formulation of the law of the excluded middle:

“Between being and nonbeing there is no middle state. Something either exists or it does not exist; there is no halfway point between the two.”

D. Q. McInerny, Being Logical: A Guide to Good Thinking, Part Two, The Basic Principles of Logic, 1. First Principles, p. 26

What these diverse formulations bring out for us is the difficulty of separating logical laws of how formal systems are to be constructed from ontological laws about how the world is constructed, and in so bringing out this difficulty, they show us the relation between the law of the excluded middle and the principle of bivalence, since the logical intuition that there are only two possible truth values of any one proposition — true or false — is so closely tied to our logical intuition that, of these two values, one or the other (but not both, which qualification is the principle of non-contradiction) must hold for any given (meaningful) proposition.

The powerful thing about Clarke’s observation is that it appeals to this admixture of logical intuitions and empirical intuitions, and in so doing seems to say something very compelling. Indeed, since I am myself a realist, and I think it can be shown that there is a fact of the matter that makes propositions true or false, I think that Clarke not only said something powerful, he also said something true: either there are extraterrestrial intelligences or there are not. It is humbling to contemplate either possibility: ourselves utterly alone in a vast universe with no other intelligent species or civilizations, or some other alien intelligence out there somewhere, unknown to us at present, but waiting to be discovered — or to discover us.

alien excluded middle 2

Although these logical intuitions are powerful, and have shaped human thought from its earliest times to the present day, the law of the excluded middle has not gone unquestioned, and indeed Clarke’s formulation gives us a wonderful opportunity to explore the consequences of the difference between constructive and non-constructive reasoning in terms of a concrete example.

To formulate the existence or non-existence of extraterrestrials in the form of a logical law like the law of the excluded middle makes the implicit realism of Clarke’s formulation obvious as soon as we think of it in these terms. In imagining the possibilities of our cosmic isolation or an unknown alien presence our terror rests on our intuitive, visceral feeling of realism, which is as immediate to us as the intuitions rooted in our own experiences as bodies.

The constructivist (at least, most species of constructivist, but not necessarily all) must deny the validity of the teritum non datur formulation of the presence of extraterrestrials, and in so doing the constructivist must pretend that our visceral feelings of realism are misleading or false, or must simply deny that these feelings exist. None of these are encouraging strategies, especially if one is committed to understanding the world by getting to the bottom of things rather than denying that they exist. Not only I am a realist, but I also believe strongly in the attempt to do justice to our intuitions, something that I have described in two related posts, Doing Justice to Our Intuitions and How to Formulate a Philosophical Argument on Gut Instinct.

In P or not-P (as well as in subsequent posts concerned with constructivism, What is the relationship between constructive and non-constructive mathematics? Intuitively Clear Slippery Concepts, and Kantian Non-constructivism) I surveyed constructivist and non-constructivist views of tertium non datur and suggested that constructivists and non-constructivists need each other, as each represents a distinct point of view on formal thought. Formal thought is enriched by these diverse perspectives.

But whereas non-constructive thought, which is largely comprised of classical realism, can accept both the constructivist and non-constructivist point of view, the many varieties of constructivism usually explicitly deny the validity of non-constructive methods and seek to systematically limit themselves to constructive methods and constructive principles. Most famously, L. E. J. Brouwer (whom I have previously discussed in Saying, Showing, Constructing and One Hundred Years of Intuitionism and Formalism) formulated the philosophy of mathematics we now know as intuitionism, which is predicated upon the explicit denial of the law of the excluded middle. Brouwer, and those following him such as Heyting, sought to formulate mathematical and logic reasoning without the use of tertium non datur.

Brouwer and the intuitionists (at least as I interpret them) were primarily concerned to combat the growing influence of Cantor and his set theory in mathematics, which seemed to them to license forms of mathematical reasoning that had gone off the rails. Cantor had gone too far, and the intuitionists wanted to reign him in. They were concerned about making judgments about infinite totalities (in this case, sets with an infinite number of members), which the law of the excluded middle, when applied to the infinite, allows one to do. This seems to give us the power to make deductions about matters we cannot either conceive or even (as it is sometimes said) survey. “Surveyability” became a buzz word in the philosophy of mathematics after Wittgenstein began using it in his posthumously published Remarks on the Foundations of Mathematics. Although Wittgenstein was not himself an intuitionist sensu stricto, his work set the tone for constructivist philosophy of mathematics.

Given the intuitionist rejection of the law of the excluded middle, it is not correct to say that there either is intelligent alien life in the universe or there is not intelligent alien life in the universe; to meaningfully make this statement, one would need to actually observe (inspect, survey) all possible locations where such alien intelligence might reside, and only after seeing it for oneself can one legitimately claim that there is or is not alien intelligence in the universe. For am example closer to home, it has been said that an intuitionist will deny the truth of the statement “either it is raining or it is not raining” without looking out the window to check and see. This can strike one as merely perverse, but we must take the position seriously, as I will try to show with the next example.

The day before the Battle of Salamis, Aristotle might have said that there would be a sea battle tomorrow or there would not be a sea battle tomorrow, and in this case the first would have been true; on other days, the second would have been true.

The day before the Battle of Salamis, Aristotle might have said that there would be a sea battle tomorrow or there would not be a sea battle tomorrow, and in this case the first would have been true; on other days, the second would have been true.

Already in classical antiquity, Aristotle brought out a striking feature of the law of the excluded middle, in a puzzle sometimes known as the “sea battle tomorrow.” The idea is simple: either there will be a sea battle tomorrow, or there will not be a sea battle tomorrow. We may not know anything about this battle, and as of today we do not even know if it will take place, but we can nevertheless confidently assert that either it will take place or it will not take place. This is the law of the excluded middle as applied to future contingents.

One way to think of this odd consequence of the law of the excluded middle is that when it is projected beyond the immediate circumstances of our ability to ascertain its truth by observation it becomes problematic. This is why the intuitionists reject it. Aristotle extrapolated the law of the excluded middle to the future, but we could just as well extrapolate it into the past. Historians do this all the time (either Alexander cut the Gordian Knot or Alexander did not cut the Gordian Knot), but because of our strong intuitive sense of historical realism this does not feel as odd as asserting that something that hasn’t happened yet either will happen or will not happen.

In terms of Clarke’s dichotomy, we could reformulate Aristotle’s puzzle about the sea battle tomorrow in terms of the discovery of alien intelligence tomorrow: either we will receive an alien radio broadcast tomorrow, or we will not receive an alien broadcast tomorrow. There is no third possibility. One way or another, the realist says, one of these propositions is true, and one of them is false. We do not know, today, which one of them is true and which one of them is false, but that does not mean that they do no possess definite truth values. The intuitionist says that the assertion today that we will or will not receive an alien radio broadcast is meaningless until tomorrow comes and we turn on our radio receivers to listen.

The intuitionists thus have an answer to this puzzling paradox that remains a problem for the realist. This is definitely a philosophical virtue for intuitionism, but, like all virtues, it comes at a price. It is not a price I am willing to pay. This path can also lead us to determinism — assuming that all future contingents have a definite truth value implies that they are set in stone — but I am also not a determinist (as I discussed in The Denial of Freedom as a Philosophical Problem), and so this intersection of my realism with my libertarian free willist orientation leaves me with a problem that I am not yet prepared to resolve. But that’s what makes life interesting.

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Grand Strategy Annex

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L. E. J. Brouwer: philosopher of mathematics, mystic, and pessimistic social theorist

A message to the foundations of mathematics (FOM) listserv by Frank Waaldijk alerted me to the fact that today, 14 October 2012, is the one hundredth anniversary of Brouwer’s inaugural address at the University of Amsterdam, “Intuitionism and Formalism.” (I have discussed Frank Waaldijk earlier in P or Not-P and What is the Relationship Between Constructive and Non-Constructive Mathematics?)

I have called this post “One Hundred Years of Intuitionism and Formalism” but I should have called it “One Hundred Years of Intuitionism” since, of the three active contenders as theories for the foundations of mathematics a hundred years ago, only intuitionism is still with us in anything like its original form. The other contenders — formalism and logicism — are still with us, but in forms so different that they no longer resemble any kind of programmatic approach to the foundations of mathematics. In fact, it could be said that logicism was gradually transformed into technical foundational research, primarily logical in character, without any particular programmatic content, while formalism, following in a line of descent from Hilbert, has also been incrementally transformed into mainstream foundational research, but primarily mathematical in character, and also without any particular programmatic or even philosophical content.

The very idea of “foundations” has come to be questioned in the past hundred years — though, as I commented a few days ago in The Genealogy of the Technium, the early philosophical foundationalist programs continue to influence my own thinking — and we have seen that intuitionism has been able to make the transition from a foundationalist-inspired doctrine to doctrine that might be called mathematical “best practices.” In contemporary philosophy of mathematics, one of the most influential schools of thought for the past couple of decades or more has been to focus not on theories of mathematics, but rather on mathematical practices. Sometimes this is called “neo-empiricism.”

Intuitionism, I think, has benefited from the shift from the theoretical to the practical in the philosophy of mathematics, since intuitionism was always about making a distinction between the acceptable and the unacceptable in logical principles, mathematical reasoning, proof procedures, and all those activities that are part of the mathematician’s daily bread and butter. This shift has also made it possible for intuitionism to distance itself from its foundationalist roots at a time when foundationalism is on the ropes.

Brouwer is due some honor for his prescience in formulating intuitionism a hundred years ago — and intuitionism came almost fully formed out of the mind of Brouwer as syllogistic logic came almost fully formed out of the mind of Aristotle — so I would like to celebrate Brouwer on this, the one hundredth anniversary of his inaugural address at the University of Amsterdam, in which he formulated so many of the central principles of intuitionism.

Brouwer was prescient in another sense as well. He ended his inaugural address with a quote from Poincaré that is well known in the foundationalist community, since it has been quoted in many works since:

“Les hommes ne s’entendent pas, parce qu’ils ne parlent pas la même langue et qu’il y a des langues qui ne s’apprennent pas.”

This might be (very imperfectly) translated into English as follows:

“Men do not understand each other because they do not speak the same language and there are languages ​​that cannot be learned.”

What Poincaré called men not understanding each other Kuhn would later and more famously call incommensurability. And while we have always known that men do not understand each other, it had been widely believed before Brouwer that at least mathematicians understood each other because they spoke the same universal language of mathematics. Brouwer said that his exposition revealed, “the fundamental issue, which divides the mathematical world.” A hundred years later the mathematical world is still divided.

For those who have not studied the foundations and philosophy of mathematics, it may come as a surprise that the past century, which has been so productive of research in advanced mathematics — arguably going beyond all the cumulative research in mathematics up to that time — has also been a century of conflict during which the idea of mathematics as true, certain, and necessary — ideas that had been central to a core Platonic tradition of Western thought — have all been questioned and largely abandoned. It has been a raucous century for mathematics, but also a fruitful one. A clever mathematician with a good literary imagination could write a mathematical analogue of Mandeville’s Fable of the Bees in which it is precisely the polyglot disorder of the hive that made it thrive.

That core Platonic tradition of Western thought is now, even as I write these lines, dissipating just as the illusions of the philosopher, freed from the cave of shadows, dissipate in the light of the sun above.

Brouwer, like every revolutionary (and we recall that it was Weyl, who was sympathetic to Brouwer, who characterized Brouwer’s work as a revolution in mathematics), wanted to do away with an old, corrupt tradition and to replace it with something new and pure and edifying. But in the affairs of men, a revolution is rarely complete, and it is, far more often, the occasion of schism than conversion.

Many were converted by Brouwer; many are still being converted today. As I wrote above, intuitionism remains a force to be reckoned with in contemporary mathematical thought in a way that logicism and formalism cannot claim to be such a force. But the conversions and subsequent defections left a substantial portion of the mathematical community unconverted and faithful to the old ways. The tension and the conflict between the old ways and the new ways has been a source of creative inspiration.

Precisely that moment in history when the very nature of mathematics was called into question became the same moment in history when mathematics joined technology in exponential growth.

Mars is the true muse of men.

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Mars, God of War and Muse of Men.

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Grand Strategy Annex

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Ludwig Wittgenstein and L. E. J. Brouwer

Brouwer and Wittgenstein were contemporaries, with the whole of Wittgenstein’s years contained within those of Brouwer’s (Wittgenstein lived 1889 to 1951 while Brouwer lived the longer life from 1881 to 1966). It is mildly ironic that even as Brouwer’s followers were playing down his mysticism and trying to extract only the mathematical content from his intuitionist philosophy (even the faithful Heyting distanced himself from Brouwer’s mysticism), Wittgenstein’s writings reached a much larger public which resulted in the mystical content of Wittgenstein’s works being played up and the early Wittgenstein himself, very much the logician following in the tradition of Frege and Russell, presented as a mystic.

Not only were Brouwer and Wittgenstein contemporaries, but we also know that Brouwer played a little-known role in Wittgenstein’s return to philosophy. After having written the Tractatus Logico-Philosophicus and then disappearing into the mountains of Austria to become a village schoolmaster in Trattenbach, some of those philosophers that continued to seek out Wittgenstein in his self-imposed exile convinced him to go to a lecture in Vienna in March 1928. The lecture was delivered by Brouwer (Brouwer gave two lectures; Wittgenstein is said to have attended one of them). Wittgenstein was said to have listened to the lecture with a surprised look on his face (sort of like G. E. Moore saying that Wittgenstein was the only student that looked puzzled at this lectures). So it may be the case that Brouwer played a pivotal role in the transition from the thought of the early Wittgenstein to the thought of the later Wittgenstein. (Matthieu Marion has argued this thesis.)

Wittgenstein’s distinction between saying and showing, a doctrine that dates from the Tractatus (cf. sections 4.113 and following), is often adduced in expositions of his alleged mysticism. According to Wittgenstein’s distinction, some things can be said but cannot be shown, while other things can be shown but cannot be said. While to my knowledge Wittgenstein never used the term “ineffable,” that which can be shown but cannot be said would seem to be a paradigm case of the ineffable. And since Wittgenstein identified a substantial portion of our experience as showable although unsayable, the ineffable seems then to play a central role in his thought. This puts Wittgenstein firmly in the company of figures like, say, St. Symeon the New Theologian (also, like Wittgenstein, an ascetic), which makes the case for his mysticism.

An extract from St. Symeon on the ineffable: “The grace of the all-holy spirit is given as earnest money of the souls pledged in marriage to Christ. Just as a woman without a pledge has no certainty that the union with the groom will occur within a certain length of time, so does the soul have no firm assurance that it will be re-united to its God and Master for all eternity. The soul cannot be certain that it will achieve this mystic, ineffable union nor that it will enjoy its inaccessible beauty if it does not have the pledge of His grace and does not consciously have that grace within.” (Krivocheine, Basil and Gythiel, Anthony P., In the Light of Christ: Saint Symeon, the New Theologian 949–1022, St. Vladimir’s Seminary Press, 1986, p. 367)

Brouwer was a bit more explicit in his doctrine of ineffability than was Wittgenstein, and he repeatedly asserted that the language of mathematics was a necessary evil that approximated but never fully captured the intuitive experience of mathematics, which he understood to be a free creation of the human mind. This comes across both in his early mystical treatise Life, Art, and Mysticism, which is pervaded by a sense of pessimism over the evils of the world (which include the evils of mathematical language), and his more technical papers offering an exposition of intuitionism as a philosophy of mathematics. But, like Wittgenstein, Brouwer does not (to my limited knowledge) actually use the term “ineffable.”

There is another ellipsis common to both Brouwer and Wittgenstein, and that is despite Brouwer’s openly professed intuitionism, which can be considered a species of constructivism (this latter is a point that needs to be separately argued, but I will only pass over it here with a single mention), and despite the strict finitism of the later Wittgenstein, which can also be considered a species of constructivism, neither Brouwer nor Wittgenstein employ Kantian language or Kantian formulations. No doubt there are implicit references to Kant in both, but I am not aware of any systematic references to Kant in the work of either philosopher. This is significant. Both Brouwer and Wittgenstein were philosophers of the European continent, where the influence of Kant remains strong even as his reputation waxes and wanes over the generations.

Kant was an early constructivist, or, rather, a constructivist before constructivism was explicitly formulated, and therefore sometimes called a proto-constructivist — although I have pointed out an obvious non-constructive dimension to Kant’s thought despite his proto-constructivism (which I do not deny, notwithstanding Kant’s non-constructive arguments in the first Critique). Kant’s classic proto-constructivist formulation is that the synthetic a priori truths of mathematics must be constructed, or “exhibited in intuition.” It is this latter idea, of a concept being exhibited in intuition, that has been particularly influential. But what does it mean? Obviously, a formulation like this has invited many interpretations.

The approaches of Brouwer and the later Wittgenstein could be considered different ways of exhibiting a concept in intuition. Brouwer, by casting out the law of the excluded middle from mathematics (at least in infinitistic contexts), assured that double negation was not equivalent to the truth simpliciter, so that even if you know that it is not the case that x is false, you still don’t know that x is true. (On the law of the excluded middle cf. P or not-P.) The later Wittgenstein’s insistence upon working out how a particular term is used and not merely settling for some schematic meaning (think of slogans like “don’t ask for the meaning, ask for the use” and “back to the rough ground”) similarly forces one to consider concrete instances rather than accepting (non-constructive) arguments for the way that things putatively must be, rather than how they are in actual fact. Both Wittgenstein’s finitism and Brouwer’s intuitionism would look with equal distaste upon, for example, proving that every set can be well-ordered without actually showing (i.e., exhibiting) such an order — also, the impossibility of exhaustively showing (i.e., exhibiting in intuition) that every set can be well-ordered if one acknowledges an infinity of sets.

I give this latter example because I think it was largely the perceived excesses of set theory and Cantor’s transfinite number theory that were essentially responsible for the reaction among some mathematicians that led to constructivism. Cantor was a great mathematical innovator, and his radical contributions to mathematics spurred foundationalists like Frege (who objected to Cantor’s methods but not his results) and Russell to attempt to construct philosophico-mathematical justifications, i.e., foundations, that would legitimize that which Cantor had wrought.

The reaction against infinitistic mathematics and foundationalism continues to the present day. Michael Dummett wrote in Elements of Intuitionism, a classic textbook on basic intuitionistic logic and mathematics, that:

“From an intuitionistic standpoint, mathematics, when correctly carried on, would not need any justification from without, a buttress from the side or a foundation from below: it would wear its own justification on its face.”

Dummett, Michael, Elements of Intuitionism, Oxford University Press, 1977, p. 2

In other words, mathematics would show its justification; in contrast, the foundationalist project to assure the legitimacy of the flights of non-constructive mathematics was wrong-headed in its very conception, because nothing that we say is going to change the fact that non-constructive thought that derives its force from proof, i.e., from what is said, does not show its justification on its face. Its justification must be established because it does not show itself. This is what “foundations” are for.

Note: There is also an element of intellectual ascesis in Dummett’s idea of a conservative extension of a theory, and this corresponds to the asceticism of Wittgenstein’s character, and, by extension, to the asceticism of Wittgenstein’s thought — asceticism being one of the clear continuities between the earlier and the later Wittgenstein — like the implicit development of constructivist themes.

But it was not only the later Wittgenstein who reacted with others against Cantor. It seems to me that the saying/showing distinction of the Tractatus is a distinction not only between that which can be said and that which can be shown, but also a distinction between that which is established by argument, possibly non-constructive argument, and that which is exhibited in intuition, i.e., constructed. If this is right, Wittgenstein showed an early sensitivity to the possibility of constructivist thought, and his later development might be understood as a development of the constructivist strand within his thinking, making Wittgenstein’s development more linear than is often recognized (though there are many scholars who argue for the unity of Wittgenstein’s development on different principles). The saying/showing distinction may be the acorn from which the oak tree of the Philosophical Investigations (and the subsequently published posthumous works) grew.

For the early Wittgenstein, the distinction between saying and showing was thoroughly integrated into his idea of logic, and while in the later sections of the Tractatus the mysticism of what which can only be shown but cannot be said becomes more evident, it is impossible to say whether it was the logical impulse that prevailed, and served as the inspiration for the mysticism, or whether it was the mystic impulse that prevailed, and served as the pretext for formulating the logical doctrines. But the logical doctrines are clearly present in the Tractatus, and serve as the exposition of Wittgenstein’s ideas, even up to the famous metaphor when Wittgenstein says that the propositions of the Tractatus are like a ladder than one must cast away after having climbed up and over it.

Just as there is a mathematical content to Brouwer’s mysticism, so too there is a logical content to Wittgenstein’s mysticism. It is, in fact, likely that Wittgenstein’s distinction between saying and showing was suggested to him by what is now called the “picture theory of meaning” given an exposition in the Tractatus. Few philosophers today defend Wittgenstein’s picture theory of meaning, but it is central to the metaphysics of the Tractatus. For Wittgenstein, the logical structure of a proposition can be shown but not said. Since for Wittgenstein in his Tractarian period, “The facts in logical space are the world” (1.13), and “In the proposition the thought is expressed perceptibly through the senses” (3.1) — i.e., the proposition literally exhibits its structure in sensory intuition — thus, “The proposition is a picture of reality.” (4.01) One might even say that a proposition exhibits the world in intuition.

Today these formulations strike us as a bit odd, because we think of anything that can be formulated in logical terms as a paradigm case of something that can be said, and very possibly also something that may not be showable. For us, logic is a language is among languages, and one way among many to express the world; for the early Wittgenstein, on the contrary, logic is the structure of the world. It shows itself because the world shows itself, and after showing itself there is nothing more to be said. The only appropriate response is silence.

As we all know from the final sentence of the Tractatus, whereof one cannot speak, thereof one must remain silent. According to the Wittgenstein of the Tractatus, all scientific questions can be asked and all scientific questions can be answered (shades of Hilbert’s “Wir müssen wissen. Wir werden wissen.” — which Per Martin-Löf has called Hilbert’s solvability axiom, and which is the very antithesis of Brouwer’s rejection of the law of the excluded middle), but even when we have answered all scientific questions, the problems of life remain untouched.

As implied by the early Wittgenstein’s insistence upon the solvability of all scientific questions, the metaphysics of Brouwer and Wittgenstein were very different. Their common constructivism does not prevent their having fundamental, I might even say foundational, differences. Also, while Wittgenstein comes across in a melancholic fashion (a lot like Plotinus, another philosophical mystic), he is not fixated on the evils of the world in the same way that Brouwer was. If both Brouwer and Wittgenstein can be called mystics, they are mystics belonging to different traditions. Brouwer was a choleric mystic while Wittgenstein was melancholic mystic.

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Grand Strategy Annex

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Last night I watched The Jane Austen Reading Club on DVD. As a film, there certainly isn’t much to recommend it. Most the characters are two-dimensional and uninteresting. There are a few good lines of dialogue here and there, but not enough to rescue this effort. Nevertheless, watching these scripted book “discussions” among the protagonists, a small circle of devoted Jane Austen readers, made me think of the origins of the Vienna Circle, which we could as well call The Ludwig Wittgenstein Reading Club.

The Vienna Circle began as a reading club, essentially, and the book they were reading was Wittgenstein’s Tractatus Logico-Philosophicus, one of the great philosophical works of the twentieth century. At once compressed and fragmented, studied and capricious, it is like a philosophical version of T. S. Eliot’s The Waste Land. In short, the Tractatus was a work to be reckoned with, and the Vienna Circle reckoned as best they could. Members of the circle read other books as well, but it was Wittgenstein’s Tractatus that was the game-changer, and Wittgenstein only published this single work during his lifetime (though he wrote much more that was posthumously published), so the Vienna Circle couldn’t choose from among a body of work (like the six Austen novels that members of the book club in the film could distribute to appropriate individuals).

Wittgenstein, on the left, wrote one of the masterpieces of twentieth century philosophy, the Tractatus Logico-Philosophicus.

Just as the members of the Jane Austen Book Club disagreed with each other and had interpretations of Austen that probably would have shocked if not saddened the author, so too the members of the Vienna Circle had interpretations of Wittgenstein that would have probably enraged Wittgenstein — and I say “enraged” in the light of many testimonials regarding his character by those who knew him well. While the Tractatus has much in it that would have appealed directly to the founders of logical positivism, there is much in the Tractatus that would have been utterly opaque to them. It is almost amusing to imagine Carnap, Neurath, and Waismann trying to elucidate the visionary and mystical sections of the book.

Wittgenstein was, by all accounts, a difficult character. There is a lot of biographical material that has been published, and it is worth reading. He was also a difficult author. It is incomprehensible to try to imagine Wittgenstein on the contemporary talk show circuit discussing the Tractatus (as amusing as the image above of Carnap discussing Wittgenstein’s mysticism). Members of the Vienna Circle tried to persuade Wittgenstein to join in discussions, mostly to no effect. Wittgenstein at one point isolated himself in the Austrian village of Trattenbach, worked as a village schoolmaster, wrote despairing letters to Bertrand Russell, and was eventually visited by Frank Ramsey, who made the pilgrimage to Trattenbach in order to discuss the Tractatus with Wittgenstein line-by-line. By that time Wittgenstein had forgotten a good deal of the context of his ideas while writing the Tractatus, and frequently had to tell the doomed Ramsey (who died young in a mountain climbing accident) that he didn’t know what he meant by a given line in the text.

Wittgenstein's philosophical manifesto: brevity is the soul of ratiocination.

When Wittgenstein returned to the world after his self-imposed exile in Trattenbach, some philosophical friends persuaded him to come to Vienna to hear a couple of lectures by Brouwer, the founder of intuitionism (one of the influential philosophies of mathematics of the period). The lectures left an impression on Wittgenstein, and the careful reader can discern Brouwer’s influence in the later Wittgenstein. Brouwer, too, was reputedly a difficult man; it seems appropriate that, among Wittgenstein’s very few influences, Brouwer should be among their number.

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The arch-atheist Jean-Paul Sartre

Despite having posted on this twice recently in A Note on Sartre’s Atheism and More on Sartre’s Atheism, I haven’t yet finished with this (as though one could ever be finished with an idea!).

I have, in a couple of posts, quoted a line from Sartre’s “Existentialism is a Humanism” lecture that ends with I must confine myself to what I can see:

I do not know where the Russian revolution will lead. I can admire it and take it as an example in so far as it is evident, today, that the proletariat plays a part in Russia which it has attained in no other nation. But I cannot affirm that this will necessarily lead to the triumph of the proletariat: I must confine myself to what I can see.

For corroboration from a fellow Frenchman and a fellow novelist consider this from Balzac’s Louis Lambert (not his most admired novel, but perhaps his most philosophical novel), delivered by the novel’s protagonist:

“To think is to see,” he said one day, roused by one of our discussions on the principle of human organization. “All science rests on deduction, — a chink of vision by which we descend from cause to effect returning upward from effect to cause; or, in a broader sense, poetry, like every work of art, springs from a swift perception of things.”

Honoré de Balzac, Louis Lambert, translated by Katharine Prescott Wormeley, Boston: Roberts Brothers, 1889, p. 39

Fellow Frenchman and philosopher Descartes offers more than corroboration: he stands at the foundation of the tradition from which both Balzac and Sartre come. In his most systematic work, the Principles of Philosophy (Book I, ix), Descartes presents an all-encompassing conception of thought, as is appropriate for the philosopher who is the locus classicus of the cogito:

By the word thought, I understand all that which so takes place in us that we of ourselves are immediately conscious of it; and, accordingly, not only to understand (INTELLIGERE, ENTENDRE), to will (VELLE), to imagine (IMAGINARI), but even to perceive (SENTIRE, SENTIR), are here the same as to think (COGITARE, PENSER). For if I say, I see, or, I walk, therefore I am; and if I understand by vision or walking the act of my eyes or of my limbs, which is the work of the body, the conclusion is not absolutely certain, because, as is often the case in dreams, I may think that I see or walk, although I do not open my eyes or move from my place, and even, perhaps, although I have no body: but, if I mean the sensation itself, or consciousness of seeing or walking, the knowledge is manifestly certain, because it is then referred to the mind, which alone perceives or is conscious that it sees or walks.

On the one hand, one can view these accounts as tributes to the visible and the tangible, except that Descartes, who stands at the origin of the tradition, can in no way be assimilated to materialism. On the other hand, and more interestingly, all of these accounts can be understood as expressions of various degrees of constructivism — mostly unconsciously formulated constructivism, but nevertheless an awareness that our thought must be disciplined by experience in a rigorous way if it is not to go terribly wrong. This is also a Kantian orientation, as we observed in Temporal Illusions, and Kant is counted as an ancestor of contemporary constructivism.

Skeptics have always demanded that truths be exhibited. We saw this in our previous posts about Sartre’s atheism, taking Doubting Thomas as the paradigm of the skeptic, who must needs touch the wounds of Christ with his own hands before he will believe that it is the same Christ who was crucified and subsequently risen.

It is a feature of constructivist thought, and most especially intuitionism, to reject the law of logic that is called (in Latin) tertium non datur or the Law of the Excluded Middle (LEM, or just EM). This simply states that, of two contradictory propositions, one of them most be true (“P or not-P“). Intuitively, it seems eminently reasonable, except that we all know of instances in ordinary experience that cannot be adequately described in a black-or-white, yes-or-no formulation. Non-constructive reasoning makes unlimited use of the law of the excluded middle, and as a consequence holds that all propositions have definite truth values even if we haven’t yet determined the truth value or even if we can’t determine the truth value. This can lead to strange consequences, like the famous Aristotelian example of the sea fight tomorrow: either there will be a sea battle tomorrow or there will not be a sea battle tomorrow. We don’t know at present which is true, but if we accept the logic of non-constructive reasoning, we will acknowledge that one of these propositions is true while the other is false.

The law of the excluded middle implies the principle of bivalence — the principle that there are two and only two logical values, namely true and false — and bivalence in turn implies realism. Realism as a philosophical doctrine stands in opposition to constructivism. Plato is the most famous realist philosopher, and believed that all kinds of things were real that common sense and ordinary experience don’t think of as being “real,” while at the same time disbelieving in the reality of the material world. Thus Plato is something of an antithesis to the kind insistence upon the tangibility and visibility upon which the skeptic and the materialist rely.

It is interesting, then, in the context of Sartre’s atheism and his insistence upon relying upon the seen, which we have now come to recognize as a kind of constructivism, to contrast the very different viewpoint represented by William James. One of James’ most famous essays is “The Will to Believe” in which he lays down the criteria for legitimate belief even where sufficient evidence is lacking. William James offers, “a defence of our right to adopt a believing attitude in religious matters, in spite of the fact that our merely logical intellect may not have been coerced.” Among the criteria that James invokes is when a choice is forced, which he describes like this:

…if I say to you: “Choose between going out with your umbrella or without it,” I do not offer you a genuine option, for it is not forced. You can easily avoid it by not going out at all. Similarly, if I say, “Either love me or hate me,” “Either call my theory true or call it false,” your option is avoidable. You may remain indifferent to me, neither loving nor hating, and you may decline to offer any judgment as to my theory. But if I say, “Either accept this truth or go without it,” I put on you a forced option, for there is no standing place outside of the alternative. Every dilemma based on a complete logical disjunction, with no possibility of not choosing, is an option of this forced kind.

Logical disjunction is another name used for the law of the excluded middle. Here James reveals himself as a realist, if not a Platonist, in matters of the spirit, just as we saw that Sartre revealed himself as a constructivist, if not an intuitionist, in matters of the spirit. The point I am making here is that this is not merely a difference of belief, but a difference in logic, and a difference in logic and reaches up into the ontology of each and informs an entire view of the world. People tend to think of logic, if they think of logic at all, as something recondite and removed from ordinary human experience, but this is not the case. Logic determines the relationship that we construct with the world, and it organizes how we see the world.

Nietzsche wrote in a famous line (or, perhaps I should say, a line that ought to be more famous than it perhaps is) that the nature and degree of an individual’s sexuality reaches into the highest pinnacles of his spirit. I agree with this, but I would add that the nature and kind of an individual’s logic — be it constructivist or non-constructivist — also reaches into the highest pinnacles of his spirit and indeed informs the world in which his spirit finds a home… or fails to find a home.

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Luigi Nono

For the six months or so that I have been posting to this forum I have been quite preoccupied with intensely practical questions in history, economics, politics, diplomacy and how these spheres of activity are related in a substantive way to human nature.

When Heilbronner wrote his famous book about economists he called them the “the worldly philosophers,” which invites an implicit comparison to unworldly or otherworldly philosophers who do not concern themselves with the ordinary business of life. Be that as it may, it is possible, I think, to be both — thinking both the worldly and the unworldly by turns. Thus is the thinker likely to experience a dialectic not only within the realms of thought, but also as part of the ordinary business of his life.

I find myself today thrown back onto the most abstruse and obscure points of technical philosophy in my attempt to clarify my understanding of very worldly concepts that attempt to elucidate what Marshall called “the ordinary business of life.” I find that I am once again taking down my reference works on ontology, epistemology, and philosophy of logic from my bookshelves, and this, I think, is a good thing. The cross-fertilization of thought, whether inter-disciplinary or intra-disciplinary, is usually a source of fruitful meditation. In particular, I find myself working on the idea of constructivism.

Constructivism means many different things to many different persons. It would almost seem that a sense of “constructivism” has been defined for every conceivable special field of inquiry or endeavor. There is constructivism in the visual arts, and a constructivism in music, and a constructivism in sociology, and, what most concerns me, a constructivism in the philosophy of logic and mathematics.

Dr. David C. F. Wright quoted his friend British composer Reginald Smith Brindle regarding a visit to Luigi Nono:

I went there mostly while he was composing Il Canto Sospeso, a politically orientated work of choral-orchestral character which involved the most abstruse constructivism I have ever come across. Mathematics governed every detail of the composition … the pitch of the notes, their duration, volume and sound character. In his study, there was a wall entirely covered with successions of numbers, notes and performance details and from this he extracted all the details of the composition. It seemed to me that all his intense constructivism was a certain formula for the creation of non-music, yet from recordings of his music, I got the impression of a highly sensitive artistry.

What Brindle describes is more commonly known as integral serialism or total serialism. The relation between constructivism and serialism is an interesting question in itself, but one that I will not address here. And while I don’t have a CD of Il Canto Sospeso, I did have a recording by the Arditti Quartet of Nono’s fragmente – stille, an idiotma, so I put this on as my theme music for constructivism.

I regard the philosophy of mathematics as the ultimate proving ground for all philosophical theories. One finds philosophical theories applied to the philosophy of mathematics in their purest form, and it is in their purest form that theories are seen in their nakedness, revealed to all the world for what they are. This is especially true for constructivism, but while constructivism is best tested by the austere ontology of logic and mathematics, it has universal implications.

Constructivism is a methodological concept, and the distinction between constructive methods and non-constructive methods recapitulates the ancient division between idealism and realism in ontology. One could say that constructivism is idealism put into practice as a method. What, then, is the method of idealism?

At present I am only trying to get clear about the concept of constructivism, its proper scope as a concept. I sent off an e-mail to the phil-logic discussion listserv and got some replies both on-list and off-list that provided some initial stimulation. It is, however, extraordinarily difficult to develop a sympathetic discussion on an e-mail listserv. Even when others are the list are interested in the idea, the tone of discussion can be brutal at times. There is a value in brutal honesty and openness of discussion, but there is also a value in having someone with whole one can share inchoate ideas and help to bring out what is valuable in them without destroying a fragile thought. However, I have no one to act as my intellectual second (i.e., kaishakunin, 介錯人) and thus I pour it out here instead.

It takes a true friend to perform the office of kaishakunin.

It takes a true friend to perform the office of kaishakunin.

I found an interesting discussion of constructivism in Detlefsen’s contribution to the Companion Encyclopedia of the History and Philosophy of the Mathematical Sciences, in which Detlefsen does try to formulate the theoretical unity of constructivism, although he never touches on predicativism. Should predicativism be considered something utterly different? There is also a great discussion of constructivism by Michael Hallett in the Handbook of Metaphysics and Ontology edited by Hans Burkhardt and Barry Smith, published by Philosophia Verlag (Hallett’s article is “mathematical objects”). While these two discussions are a great starting point, they don’t get to the essence of the question that is troubling me at the moment.


The many varieties of constructivism are different not only in detail but also importantly different in conceptual scope. Intuitionism, finitism, predicativism, and other conceptions that might generally be called constructivistic in tendency all restrict classical formal reasoning, but there does not seem to be any prima facie unity in virtue of which all deserve to be called constructivist. One of my off-list responses from the phil-logic listserv suggested that there would be “push back” at any attempt to classify intuitionism as a form of constructivism.

handbook of metaphysics and ontology

James Robert Brown’s The Philosophy of Mathematics: An Introduction to the World of Proofs and Pictures has a section on “Constructivist Approaches” that quotes from Errett Bishop’s Foundations of Constructive Analysis. I don’t have a copy of Bishop’s book, so this is helpful. Bishop, at least, explicitly identifies his approach as constructivist, unlike Brouwer or Heyting, Poincare or Weyl, Yesnin-Volpin and Gauthier, Kielkopf and Wittgenstein. This self-ascribed constructivist identity carries more weight than all the other uses of “constructivist” combined.

James Robert Brown

Perhaps constructivism in its pure form should be defined more narrowly, strictly in terms of the avoidance of pure existence proofs, for example. But if we define constructivism more narrowly, then it would seem that there is still a need for a concept under which would fall all those theories of formal reason that restrict what Torkel Franzen called “classical eclectism,” and which would include a narrowly defined constructivism as well as other doctrines previously called constructivist. What concept could we use to cover all instances of principled restrictions upon formal reasoning, and is there any unity of motive in formulating and propounding principled limitations on formal reasoning?

The obvious course of action would be to elucidate the principles embodied in all such doctrines, loosely called “constructivist” up until now, and seek to systematically interrelate them. In every police drama one sees on television, the detectives on a difficult case assemble a large bulletin board upon which they display symbols for clues, and then map the interrelations between clues in an attempt to find a pattern that will solve the case. We need the conceptual equivalent of this in order to understand constructivism.

Two other obvious courses of action present themselves: simultaneously driving down into the foundations of constructivist doctrines while also extrapolating their consequences to the utmost limit. A convergence or divergence of either development would point to fundamental commonality or fundamental incommensurability.

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