First published in 1908 as the second edition of a 1900 original, this book explains the content of the fifth and sixth books of Euclid's Elements, which are primarily concerned with ratio and magnitudes. Hill furnishes the text with copious diagrams to illustrate key points of Euclidian reasoning. This book will be of value to anyone with an interest in the history of education.

(Translation of Frege's Grundgesetze II, §§ 86-137).

Plato believed that behind everything in the universe lie mathematical principles. Plato was inspired by Pythagoras (571 BCE), who developed a school of mathematics at Crotona that studied sacred geometry as a form of religion. The school’s motto was “God is number,” or “All is Number”. Pythagoras believed that numbers represented God in pattern, symmetry, and infinity. When one of its students, Hippasus told the world the secret of the existence of irrational numbers, Greek geometry was born (...) and Pythagoras’ idea of divinity in numbers died because how could God not be perfect and symmetrical? In Plato’s Republic he discusses something called The Divided Line, which is a map, of sorts, for reaching what he calls the highest Good, which is the ultimate truth where one realizes the true state of the universe and can see the world for what it really is. Many mathematicians have attempted to plot Plato’s Divided Line only to come across a litany of problems and conundrums. Some have said that it the Divided Line cannot be plotted and is merely an allegory not meant to be plotted. This paper discusses some of the conundrums preventing the plotting of Plato’s Divided Line (not an exhaustive list), including Whole ‘vs’ Separate, Equality ‘vs’ Ontological Dissimilarity, Linear ‘vs’ Non-linear, and Infinity ‘vs’ Finite. This paper also explores a new understanding of the Allegory of the Cave in light of ‘the problem of the irrational.’ In exploring the link between the Divided Line and the ‘the problem of the irrational,’ I was able to plot it. It was found that the Divided Line is not a line in the linear sense, but a spiral, the Golden Ratio! This paper is an example of a new category of scholarly inquiry I call “Math Theory” based on scholarly mathematical axioms in theory, rather than including actual maths. In my papers I use existing mathematical equations and place them in an encompassing theory, rather than finding new formulae to fit an existing theory. Keywords: Pythagoras, divided line, math theory, highest good, all is number. (shrink)

ABSTRACT Because the modern concept of number emerged within a quadrivium that included music alongside arithmetic, geometry, and astronomy, musical considerations affected mathematical developments. Michael Stifel embedded the then‐paradoxical term “irrational numbers” (numerici irrationales) in a musical context (1544), though his philosophical aversion to the “cloud of infinity” surrounding such numbers finally outweighed his musical arguments in their favor. Girolamo Cardano gave the same status to irrational and rational quantities in his algebra (1545), for which his (...) contemporaneous work on music suggested parallels and empirical examples. Nicola Vicentino's attempt to revive ancient “enharmonic” music (1555) required and hence defended the use of “irrational proportions” (proportiones inrationales) as if they were numbers. These developments emerged in richly interactive social and cultural milieus whose participants interwove musical and mathematical interests so closely that their intense controversies about ancient Greek music had repercussions for mathematics as well. The musical interests of Stifel, Cardano, and Vicentino influenced their respective treatments of “irrational numbers.” Practical as well as theoretical music both invited and opened the way for the recognition of a radically new concept of number, even in the teeth of paradox. (shrink)

In his early philosophy as well as in his middle period, Wittgenstein holds a purely syntactic view of logic and mathematics. However, his syntactic foundation of logic and mathematics is opposed to the axiomatic approach of modern mathematical logic. The object of Wittgenstein’s approach is not the representation of mathematical properties within a logical axiomatic system, but their representation by a symbolism that identifies the properties in question by its syntactic features. It rests on his distinction of descriptions and operations; (...) its aim is to reduce mathematics to operations. This paper illustrates Wittgenstein’s approach by examining his discussion of irrational numbers. (shrink)

A moderately risk averse person may turn down a 50/50 gamble that either results in her winning $200 or losing $100. Such behaviour seems rational if, for instance, the pain of losing $100 is felt more strongly than the joy of winning $200. The aim of this paper is to examine an influential argument that some have interpreted as showing that such moderate risk aversion is irrational. After presenting an axiomatic argument that I take to be the strongest case (...) for the claim that moderate risk aversion is irrational, I show that it essentially depends on an assumption that those who think that risk aversion can be rational should be skeptical of. Hence, I conclude that risk aversion need not be irrational. (shrink)

On a now orthodox view, humans and many other animals possess a “number sense,” or approximate number system, that represents number. Recently, this orthodox view has been subject to numerous critiques that question whether the ANS genuinely represents number. We distinguish three lines of critique – the arguments from congruency, confounds, and imprecision – and show that none succeed. We then provide positive reasons to think that the ANS genuinely represents numbers, and not just non-numerical confounds or exotic substitutes (...) for number, such as “numerosities” or “quanticals,” as critics propose. In so doing, we raise a neglected question: numbers of what kind? Proponents of the orthodox view have been remarkably coy on this issue. But this is unsatisfactory since the predictions of the orthodox view, including the situations in which the ANS is expected to succeed or fail, turn on the kind of number being represented. In response, we propose that the ANS represents not only natural numbers, but also non-natural rational numbers. It does not represent irrational numbers, however, and thereby fails to represent the real numbers more generally. This distances our proposal from existing conjectures, refines our understanding of the ANS, and paves the way for future research. (shrink)

A popular view is that the great discovery of Pythagoras was that there are irrational numbers, e.g., the positive square root of two. Against this it is argued that mathematics and geometry, together with their applications, do not show that there are irrational numbers or compel assent to that proposition.

First published in 1997, this volume originated from an article published in Ratio and reapproaches Aristotle in an attempt to define what counts as an irrational action, along with a general account of irrationality based on a large number of specific examples. It begins with Aristotle, and never leaves him far behind. Contemplating akrasia, will, self-knowledge and commensurability, the author demonstrates that we must allow for the possibility of breakdown in cases where someone may fail to do the rational (...) action through weakness of will and that to make sense of akrasia we must be ready to allow for distinct cases. (shrink)

ArgumentFrom the time of al-Khwārizmī in the ninth century to the beginning of the sixteenth century algebraists did not allow irrational numbers to serve as coefficients. To multiply$\sqrt {18} $byx, for instance, the result was expressed as the rhetorical equivalent of$\sqrt {18{x^2}} $. The reason for this practice has to do with the premodern concept of a monomial. The coefficient, or “number,” of a term was thought of as how many of that term are present, and not as (...) the scalar multiple that we work with today. Then, in sixteenth-century Europe, a few algebraists began to allow for irrational coefficients in their notation. Christoff Rudolff was the first to admit them in special cases, and subsequently they appear more liberally in Cardano, Scheubel, Bombelli, and others, though most algebraists continued to ban them. We survey this development by examining the texts that show irrational coefficients and those that argue against them. We show that the debate took place entirely in the conceptual context of premodern, “cossic” algebra, and persisted in the sixteenth century independent of the development of the new algebra of Viète, Decartes, and Fermat. This was a formal innovation violating prevailing concepts that we propose could only be introduced because of the growing autonomy of notation from rhetorical text. (shrink)

Most deontologists find bedrock in the Pauline doctrine that it is morally objectionable to do evil in order that good will come of it. Uncontroversially, this doctrine condemns the killing of an innocent person simply in order to maximize the sum total of happiness. It rules out the conscription of a worker to his or her certain death in order to repair a fault that is interfering with the live broadcast of a World Cup match that a billion spectators have (...) been enjoying. It rules out such sacrifice even if it would maximize the sum total of everyone's happiness. An act utilitarian, by contrast, would require the sacrifice of the one whenever this latter condition obtains, since such a utilitarian is committed to the view that one ought always to act so as to bring about the greatest sum total of happiness. An act utilitarian might, however, consistently hold that a large number of rather insignificant pleasures, such as that which a spectator derives from witnessing men in shorts running around and kicking a ball, is never sufficient to justify the infliction of a great harm on a single individual. 4 He might take such a position without abandoning utilitarianism by denying that the sum total of such minor pleasures could ever be sufficiently great to outweigh the harm of death to the one. Under the inspiration of John Stuart Mill, a utilitarian might draw a more general distinction between serious and trivial harms and pleasures and maintain that no amount of a trivial pleasure could ever amount to a sum of happiness that is greater than the disutility of a serious harm. (shrink)

Utilitarian deliberation has a number of weak or open points where the agent's judgements tend to be influenced by psychological and sociological factors, e.g., by his prejudices, anxieties, insecurities or group-identifications. The most vulnerable points are: the formulation of the problem, the selection of alternatives, the calculation of consequences, the weighing of evidence, the selection of ultimate values and the comparison of different values towards each other.— The utilitarian vocabulary provides the chooser with misleading expressions such as "The action A1 (...) produces more value on the whole than A2" backing up his cpnviction of acting rationally. — In order to improve the situation, we must become aware of the delusiveness of such expressions and of society's and our own irrationality and try to develop more rational feelings and attitudes. (shrink)

Most deontologists find bedrock in the Pauline doctrine that it is morally objectionable to do evil in order that good will come of it. Uncontroversially, this doctrine condemns the killing of an innocent person simply in order to maximize the sum total of happiness. It rules out the conscription of a worker to his or her certain death in order to repair a fault that is interfering with the live broadcast of a World Cup match that a billion spectators have (...) been enjoying. It rules out such sacrifice even if it would maximize the sum total of everyone's happiness. An act utilitarian, by contrast, would require the sacrifice of the one whenever this latter condition obtains, since such a utilitarian is committed to the view that one ought always to act so as to bring about the greatest sum total of happiness. An act utilitarian might, however, consistently hold that a large number of rather insignificant pleasures, such as that which a spectator derives from witnessing men in shorts running around and kicking a ball, is never sufficient to justify the infliction of a great harm on a single individual. 4 He might take such a position without abandoning utilitarianism by denying that the sum total of such minor pleasures could ever be sufficiently great to outweigh the harm of death to the one. Under the inspiration of John Stuart Mill, a utilitarian might draw a more general distinction between serious and trivial harms and pleasures and maintain that no amount of a trivial pleasure could ever amount to a sum of happiness that is greater than the disutility of a serious harm. (shrink)

Utilitarian deliberation has a number of weak or open points where the agent's judgements tend to be influenced by psychological and sociological factors, e.g., by his prejudices, anxieties, insecurities or group-identifications. The most vulnerable points are: the formulation of the problem, the selection of alternatives, the calculation of consequences, the weighing of evidence, the selection of ultimate values and the comparison of different values towards each other.— The utilitarian vocabulary provides the chooser with misleading expressions such as "The action A1 (...) produces more value on the whole than A2" backing up his cpnviction of acting rationally. — In order to improve the situation, we must become aware of the delusiveness of such expressions and of society's and our own irrationality and try to develop more rational feelings and attitudes. (shrink)

Most deontologists find bedrock in the Pauline doctrine that it is morally objectionable to do evil in order that good will come of it. Uncontroversially, this doctrine condemns the killing of an innocent person simply in order to maximize the sum total of happiness. It rules out the conscription of a worker to his or her certain death in order to repair a fault that is interfering with the live broadcast of a World Cup match that a billion spectators have (...) been enjoying. It rules out such sacrifice even if it would maximize the sum total of everyone's happiness. An act utilitarian, by contrast, would require the sacrifice of the one whenever this latter condition obtains, since such a utilitarian is committed to the view that one ought always to act so as to bring about the greatest sum total of happiness. An act utilitarian might, however, consistently hold that a large number of rather insignificant pleasures, such as that which a spectator derives from witnessing men in shorts running around and kicking a ball, is never sufficient to justify the infliction of a great harm on a single individual. 4 He might take such a position without abandoning utilitarianism by denying that the sum total of such minor pleasures could ever be sufficiently great to outweigh the harm of death to the one. Under the inspiration of John Stuart Mill, a utilitarian might draw a more general distinction between serious and trivial harms and pleasures and maintain that no amount of a trivial pleasure could ever amount to a sum of happiness that is greater than the disutility of a serious harm. (shrink)

Since independence, at least 28 African countries have legalized some form of gambling. Yet a range of informal gambling activities have also flourished, often provoking widespread public concern about the negative social and economic impact of unregulated gambling on poor communities. This article addresses an illegal South African numbers game called fahfee. Drawing on interviews with players, operators, and regulatory officials, this article explores two aspects of this game. First, it explores the lives of both players and runners, as (...) well as the clandestine world of the Chinese operators who control the game. Second, the article examines the subjective motivations and aspirations of players, and asks why they continue to play, despite the fact that their aggregate losses easily outstrip their aggregate gains. In contrast with those who reduce its appeal simply to the pursuit of wealth, I conclude that, for the (mostly) black, elderly, working class women who play fahfee several times a week, the associated trade-off—regular, small losses, versus the social enjoyment of playing and the prospect of occasional but realistic windfalls—takes on a whole new meaning, and preferences for relatively lumpy rather than steady consumption streams help explain the continued attraction of fahfee. This reinforces the need to understand players’ own accounts of gambling utility rather than simply to moralistically condemn gambling or to dismiss gamblers behaviour as irrational. (shrink)

Numbers. Natural numbers -- Integers -- Real numbers -- Irrational and transcendental numbers -- Funny numbers. Zero -- e : the unnatural natural number -- [Phi] : the golden ratio -- i : the imaginary number -- Writing numbers. Roman numerals -- Egyptian fractions -- Continued fractions -- Logic. Mr. Spock is not logical -- Proofs, truth, and trees : oh my! -- Programming with logic -- Temporal reasoning -- Sets. Cantor's diagonalization : (...) infinity isn't just infinity -- Axiomatic set theory : keep the good, dump the bad -- Models : using sets as the LEGOs of the math world -- Transfinite numbers : counting and ordering infinite sets -- Group theory : finding symmetries with sets -- Mechanical math. Finite state machines : simplicity goes far -- The turing machine -- Pathology and the heart of computing -- Calculus : no, not that calculus- [lambda] calculus -- Numbers, booleans, and recursion -- Types, types, types : modeling [lambda] calculus -- The halting problem. (shrink)

Most deontologists find bedrock in the Pauline doctrine that it is morally objectionable to do evil in order that good will come of it. Uncontroversially, this doctrine condemns the killing of an innocent person simply in order to maximize the sum total of happiness. It rules out the conscription of a worker to his or her certain death in order to repair a fault that is interfering with the live broadcast of a World Cup match that a billion spectators have (...) been enjoying. It rules out such sacrifice even if it would maximize the sum total of everyone's happiness. An act utilitarian, by contrast, would require the sacrifice of the one whenever this latter condition obtains, since such a utilitarian is committed to the view that one ought always to act so as to bring about the greatest sum total of happiness. An act utilitarian might, however, consistently hold that a large number of rather insignificant pleasures, such as that which a spectator derives from witnessing men in shorts running around and kicking a ball, is never sufficient to justify the infliction of a great harm on a single individual. 4 He might take such a position without abandoning utilitarianism by denying that the sum total of such minor pleasures could ever be sufficiently great to outweigh the harm of death to the one. Under the inspiration of John Stuart Mill, a utilitarian might draw a more general distinction between serious and trivial harms and pleasures and maintain that no amount of a trivial pleasure could ever amount to a sum of happiness that is greater than the disutility of a serious harm. (shrink)

Some irrational numbers are "random" in a sense which implies that no algorithm can compute their decimal expansions to an arbitrarily high degree of accuracy. This feature of (most) irrational numbers has been claimed to be at the heart of the deterministic, but chaotic, behavior exhibited by many nonlinear dynamical systems. In this paper, a number of now classical chaotic systems are shown to remain chaotic when their domains are restricted to the computable real numbers, (...) providing counterexamples to the above claim. More fundamentally, the randomness view of chaos is shown to be based upon a confusion between a chaotic function on a phase space and its numerical representation in Rn. (shrink)

We show that if is not in the field generated by α1,…,αn, then no restriction of the function xβ to an interval is definable in . We also prove that if the real and imaginary parts of a complex analytic function are definable in Rexp or in the expansion of by functions xα, for irrational α, then they are already definable in . We conclude with some conjectures and open questions.

La question au nombre irrationnel et de l'irrationnel mathématique en général, tient une part discrète dans l'oeuvre de Platon, mais elle est comme cette "pierre délaissée par les architectes" et qui est pourtant "la pierre angulaire". Elle concentre toutes les questions de l'être et du non-être, du possible et de l'impossible, du fini et de l'infini et ouvre la voie à la liberté pleine et entière de l'homme en quête de vérité. En elle, convergent pensée mathématique et spéculation philosophique, en (...) une harmonie riche de conséquences inestimables. C'est cette harmonie que révèle Imre Toth dans un essai brillant et rigoureux, le dernier qu'il ait écrit avant sa brusque disparition en mai 2010. "Les Editions de l'éclat viennent de contribuer à réparer ce qui apparaît comme une lacune de l'édition française en publiant deux textes récents d'Imre Toth" - Françoise Balibar (Critique). "Le livre de Toth est extrêmement séduisant, croisant la polémique politique la plus vive avec l'initiation limpide aux problèmes fondamentaux de la philosophie des mathématiques" - Jean-Paul Thomas (Le Monde). "Philosophes comme historiens des sciences pourront tirer profit de ce regard enflammé sur le processus mathématique, qui place la liberté au coeur de la création, mais va au-delà en cherchant à comprendre son fonctionnement, précisément en mathématique" - Jean-Michel Kantor (La Quinzaine littéraire). (shrink)

We study in a constructive manner some problems of topology related to the set Irr of irrational reals. The constructive approach requires a strong notion of an irrational number; constructively, a real number is irrational if it is clearly different from any rational number. We show that the set Irr is one-to-one with the set Dfc of infinite developments in continued fraction . We define two extensions of Irr, one, called Dfc1, is the set of dfc of (...) rationals and irrationals preserving for each rational one dfc, the other, called Dfc2, is the set of dfc of rationals and irrationals preserving for each rational its two dfc. We introduce six natural distances over Irr wich we denote by dfc0, dfc1, dfc2, d, dmir and dcut. We show that only the four distances dfco, dfc1, d and dmir among the six make Irr a complete metric space. The last distances define in Irr the same topology in a constructive sens. We study further the set Dfc1 in which we show that the irrationals constitute a closed subset. Finally, we make a particular study of the completion Dfc2 of Dfc for the two equivalent metrics dfc2 and dcut. (shrink)

Deleuze's theory of time set out in Difference and Repetition is a complex structure of three different syntheses of time – the passive synthesis of the living present, the passive synthesis of the pure past and the static synthesis of the future. This article focuses on Deleuze's third synthesis of time, which seems to be the most obscure part of his tripartite theory, as Deleuze mixes different theoretical concepts drawn from philosophy, Greek drama theory and mathematics. Of central importance is (...) the notion of the cut, which is constitutive of the third synthesis of time defined as an a priori ordered temporal series separated unequally into a before and an after. This article argues that Deleuze develops his ordinal definition of time with recourse to Kant's definition of time as pure and empty form, Hölderlin's notion of ‘caesura’ drawn from his ‘Remarks on Oedipus’ (1803) and Dedekind's method of cuts as developed in his pioneering essay ‘Continuity and Irrational Numbers’ (1872). Deleuze then ties together the conceptions of the Kantian empty form of time and the Nietzschean eternal return, both of which are essentially related to a fractured I or dissolved self. This article aims to assemble the different heterogeneous elements that Deleuze picks up on and to show how the third synthesis of time emerges from this differential multiplicity. (shrink)

In the framework of the De Regula Aliza, Cardano paid much attention to the so-called splittings for the family of equations $$x^3 = a_1x + a_0$$ x3=a1x+a0 ; my previous article deals at length with them and, especially, with their role in the Ars Magna in relation to the solution methods for cubic equations. Significantly, the method of the splittings in the De Regula Aliza helps to account for how Cardano dealt with equations, which cannot be inferred from his other (...) algebraic treatises. In the present paper, this topic is further developed, the focus now being directed to the origins of the splittings. First, we investigate Cardano’s research in the Ars Magna Arithmeticae on the shapes for irrational solutions of cubic equations with rational coefficients and on the general shapes for the solutions of any cubic equation. It turns out that these inquiries pre-exist Cardano’s research on substitutions and cubic formulae, which will later be the privileged methods for dealing with cubic equations; at an earlier time, Cardano had hoped to gather information on the general case by exploiting analogies with the particular case of irrational solutions. Accordingly, the Ars Magna Arithmeticae is revealed to be truly a treatise on the shapes of solutions of cubic equations. Afterwards, we consider the temporary patch given by Cardano in the Ars Magna to overcome the problem entailed by the casus irreducibilis as it emerges once the complete picture of the solution methods for all families of cubic equations has been outlined. When Cardano had to face the difficulty that appears if one deals with cubic equations using the brand-new methods of substitutions and cubic formulae, he reverted back to the well-known inquiries on the shape of solutions. In this way, the relation between the splittings and the older inquiries on the shape of solutions comes to light; furthermore, this enables the splittings to be dated 1542 or later. The last section of the present paper then expounds the passages from the Aliza that allow us to trace back the origins of the substitution $$x = y + z$$ x=y+z, which is fundamental not only to the method of the splittings but also to the discovery of the cubic formulae. In this way, an insight into Cardano’s way of dealing with equations using quadratic irrational numbers and other selected kinds of binomials and trinomials will be provided; moreover, this will display the role of the analysis of the shapes of solutions in the framework of Cardano’s algebraic works. (shrink)

The concept of quantity (Größe) plays a key role in Frege's theory of real numbers. Typically enough, he refers to this theory as ?theory of quantity? (?Größenlehre?) in the second volume of his opus magnum Grundgesetze der Arithmetik (Frege 1903). In this essay, I deal, in a critical way, with Frege's treatment of the concept of quantity and his approach to analysis from the beginning of his academic career until Frege 1903. I begin with a few introductory remarks. In (...) Section 2, I first analyze Frege's use of the term ?source of knowledge? (?Erkenntnisquelle?) with particular emphasis on the logical source of knowledge. The analysis includes a brief comparison between Frege and Kant's conceptions of logic and the logical source of knowledge. In a second step, I examine Frege's theory of quantity in Rechnungsmethoden, die sich auf eine Erweiterung des Größenbegriffes gründen (Frege 1874). Section 3 contains a couple of critical observations on Frege's comments on Hankel's theory of real numbers in Die Grundlagen der Arithmetik (Frege 1884). In Section 4, I consider Frege's discussion of the concept of quantity in Frege 1903. Section 5 is devoted to Cantor's theory of irrational numbers and the critique deployed by Frege. In Section 6, I return to Frege's own constructive treatment of analysis in Frege 1903 and succinctly describe what I take to be the quintessence of his account. (shrink)

This paper is concerned with the influence that the set theory of Georg Cantor bore upon the mathematical logic of Bertrand Russell. In some respects the influence is positive, and stems directly from Cantor's writings or through intermediary figures such as Peano; but in various ways negative influence is evident, for Russell adopted alternative views about the form and foundations of set theory. After an opening biographical section, six sections compare and contrast their views on matters of common interest; (...) class='Hi'>irrational numbers, infinitesimals, cardinal and ordinal numbers, the axiom of infinity, the paradoxes, and the axioms of choice. Two further sections compare the two men over more general questions: the role of logic and the philosophy of mathematics. In a final section I draw some conclusions. (shrink)

Logic in Action/Doron Avital Nothing is more difficult, and therefore more precious, than to be able to decide (Napoleon Bonaparte) Introduction -/- This book was born on the battlefield and in nights of secretive special operations all around the Middle East, as well as in the corridors and lecture halls of Western Academia best schools. As a young boy, I was always mesmerized by stories of great men and women of action at fateful cross-roads of decision-making. Then, like as today, (...) I felt the full weight of the moment of truth as it confronts the individual, the man or woman of action, with the imminent necessity to decide. Alongside, as I was climbing up the ladder of education, I found myself just as well captivated by the great intellectual stories of our times, in particular 20th century analytic philosophy and, at its core, the machinery of modern logic. How do then the cool contemplative modes of the philosophical and analytic outlooks, that are better fitting of the philosopher's armchair at the fireplace, hang together with the heat of the battlefield or the angst of the ticking clock of time left to the completion of a daring special operation? Growing up I was pondering exactly that. Not accidently, and in fact as consequence, I have chosen a course in life that challenged me to visit the poles of both theory and practice. I set myself on a mission to unravel the tension between the contemplative inquiry, supposedly theoretical, aiming at the logical structure of things, and the uncompromising test of life and action. The puzzle of the gap between theory and practice has become ever since the guiding question of my life. -/- Not long ago, I met two friends, Avner Shor, a veteran combat soldier of the special forces unit I eventually commanded, and Aviram Halevi, a fellow officer with whom I served. Why will we not put into writing the ideas that guided us during our years of military action, we wondered. At that time, I used to deliver the keynote lectures to the senior officers' course of Israel central intelligence organization, the Mossad. For this I already had to put some of these ideas in writing. Avner was quick to introduce me with a notable publisher and even helped me write the first chapter. With Aviram I sat to many meetings, where he would challenge me with key questions, and we followed them with memories of operations and battles, aiming to draw the required lessons. This served me well when I finally sat down to write the first draft of the book. The result was more extensive than me and my friends had expected. I had to add a particularly long chapter dealing with the story of modern philosophy and logic. This was required, I felt, as no decision-making process lives in an intellectual vacuum. Knowingly or subconsciously, the intellectual climate of the time guides us for better or worse with the decisions we finally take. The initial draft was naturally cumbersome and inaccessible. But here I had the privilege of meeting a particularly talented editor, Rami Rothholtz. I found in Rami both an editor and a critical reader. As an infantry combat soldier at youth and now a senior journalist and editor, Rami insisted on simplifying and refining my ideas. Had it not been for his work, this book would have been literally unreadable. *** I opened my book with a brief description of a single night of a special operation deep at the Lebanon Bekaa valley, far away from Israel northern border. The mission was to kidnap a senior terror leader known to be holding in captivity an Israeli pilot. This was also the last special operation I commanded in my military career. A single special operation night, but what had to precede it? For sure, many months of intense and skillful preparations. What is Planning? This is the question with which I open up chapter (2) of the book. I confront in this chapter two approaches to planning. The first is the one I saw as a mission to myself to cultivate in my many years of military service. The second is the one I saw as representing a deep-rooted fallacy that holds a firm grip on today's conventional wisdom about planning. To further examine the logic of the competing models, I was required in chapter (3) to analyze the concept of "The Standard". I argue that the false model of planning has its roots in an attitude of an uncompromising adherence to the power of literal obedience to standards and rules. The standard, or what is outlined by a rule as prescribing a future course of action, is seen as an answer to the fundamental tension between theory (planning) and practice (execution). I argue in contrast that the standard does not produce an answer but rather what I call: "A Well-Defined Question". In essence, it is a meticulously-well-planned invitation to exercise a fresh judgment. A judgement that has as an anchor the default answer that the standard produces but is open to extension as it confronts the new frame of reference of the test of reality. In chapter (4), I present a new tool for planning and execution: "The Polygon of Risks" or "The Polygon of Execution". The Polygon is a geometric illustration of the underlying tension that exists between all dimensions of the operational project. The construction and conceptualization of the trade-offs that exist between the various dimensions - segments of the polygon - is the first topic on the planner's agenda. I position the concepts of "Daring" and "Taking Proactive and Well-Informed Risks" as necessary logical constituents of the polygon and show how in contrast the false model of planning is responsible for an operational culture that is risk-averse. It encourages, in fact, the piling up of false securities at the segments' level that eventually lead to the collapse of the polygon. The necessary trade-offs relationships that exist between the segments of the polygon express the fundamental tension between partnership and competition: partnership in a joint goal and competition over resources, both material and abstract. When this tension is not managed well, that is, when the players' local optimizations overshadow the global optimization required for the success of the project, the execution polygon collapses. In this scenario, we may find the setting of the bar of "High Standards" in a players' spheres of responsibility to conceal a hidden agenda of personal insurances taken against a possible failure. Once the overall risk is not mitigated by way of collaborative joint executional dialogue, the process that leads to a collapse of the polygon is literally unstoppable. *** In chapter (5), I discuss "(Fateful) Decisions". I examine the way in which we should translate the polygon into sequential critical decisions on the timeline. The execution polygon is not a rigid scaffolding but a dynamic conceptual illustration of the -/- project. It will need now to be converted into successive decision junctions. We will find the content of a decision and its timing on the timeline to be inseparable. The right decision is the one that is taken at the right time. The moment of decision is in fact the last moment of deliberation, the first moment available for action, i.e. the first possible "Can" is also the latest possible "Must". Deciding too soon is analog to the "Jumping of the Gun". The decision maker is forcing a pre-conceived answer to a state of affairs not ripe for an answer, e.g. the target in the shooting range is not yet erected. Late to decide and the decision maker may envision what he or she should have done but reality is no longer available for them to harness it right, e.g. consider a tennis player's frustration when reviewing a too-late-to-react move in the video replay. I review in this chapter many fateful decisions, both historical, from Napoleon's Waterloo, to a Bridge Too Far of WWII, to the failed rescue attempt of American hostages at the time of the Iranian Revolution, as well as fateful decisions I had to take in the course of my military life, both in combat and in special operations, and show the sense in which they all answer to our analysis. The theme of chapter (6) is "The Moment of Truth". This is the moment when everything is on the line and from which there is no turning back. I discuss the formative repetitive structure of the schooling and simulation phase and contrast it with the "One Shot, One Opportunity" nature of the moment of truth. This is extremely helpful when we analyze the logical structure of failures as unwarranted repetitions of past lessons. The schooling curriculum indeed consists of important abstractions drawn from lessons of the past. However, it is when we project them in a fashion that is literal or mechanical that we cross path with the possibility of a failure. The paradox of education is that what we must repeat in school and simulation must be extended and not repeated in real life. What is required of us so we do not fall into the fallacy of repetition in face of the moment of truth is the core subject of the discussion of this chapter. In chapter (7), I took a lengthy philosophical detour surveying the intellectual drama of modern logic, and in general, the story of 20th century analytic philosophy. Readers who choose to bypass the somehow demanding narrative of this drama can do so and still keep the argumentative thread of the book. However, even by way of skipping the more technical parts, I would still urge the readers to delve into the discussion in this chapter as I believe this would grant them a deeper understanding of the overall conceptual framework. I explore here the work of two key figures: the logician Kurt Gödel and the philosopher Ludwig Wittgenstein, both were crowned in 2000 by TIME Magazine, as the leading Logician and Philosopher, respectively, of the 20th Century. I review the fascinating logical result of Gödel's Incompleteness Theorem and examine its relevance as setting a theoretical limit to the power of formalization. This amazing logical result - a result that shakes the logical foundations of 20th century thought in as much as the discovery of irrational numbers shook the foundations of the Pythagorean program of the ancient Greeks - bears significantly on the question of action and the blind trust we place in the power of formalization in the form of protocols and rules. It is here that Wittgenstein's philosophy enters in full force. We follow Wittgenstein as he dismantles our conception of rules as if there were "Railroads to Infinite", i.e. as prescribing for us in-advance their proper employments in all possible -/- future eventualities. Instead we propose that the dilemma of action demands of us an extension of rules rather than a mechanical or blind repetition of their literal imperative. In turn, this extension can serve as a new lesson added to the curriculum of school and simulation. The theme of chapter (8), the concluding chapter, is Strategy, Logic, and Ethics. The chapter comes to place the ethical dilemma in the conceptual map we presented in the book. I discuss here the tension between strategy as a process of setting goals and deriving backward as it were the steps that are necessary for achieving these goals, to the inescapable dictation of the ethical imperative. This unavoidable tension is particularly important against the backdrop of contemporary culture that is guided by a vision of personal success and achievement that may threaten our ability to do what is right. Most of all, I am troubled in this chapter, with the role logic may play, first as a liberating force enabling a change that is tuned to the ethical imperative, and second, as a force designed to justify on logical grounds, as it were, the existing power structure. It is in this junction that brave individuals will be called to challenge the governing logic of the zeitgeist - logic that operates now as an oppressive force that serves the vested interest of beneficials of the existing order. When success is favored over doing what is right, as we must admit is the prevailing cultural mood of our times, that the words of Emanuel Kant carry their full weight: "Do the Right thing and leave the Consequences to God". For this we need heroes and heroines that challenge the time by bearing the full weight of responsibility that comes with the doing of what is Right. *** This book was written more than anything from the perspective of the heroes and heroines of action. Sometimes they may be missing the exact words or the full insight into the solid logical complexity that stands between them and the doing of what is right. They feel what is right to do on the battlefield of life, whether in real battle, in political or economic life or whether in the life of creativity and the quest of the intellect. They do need, in analogy, proper logical and intellectual artillery. I hope they will find the logical cannons they require as they travel through the pages of this book. The rest is in their hands at the Moment of Truth. -/- Doron Avital, Tel Aviv 2011 -/- . (shrink)

Drawing mainly from the Tractatus Logico-Philosophicus and his middle period writings, strategic issues and problems arising from Wittgenstein’s philosophy of mathematics are discussed. Topics have been so chosen as to assist mediation between the perspective of philosophers and that of mathematicians on their developing discipline. There is consideration of rules within arithmetic and geometry and Wittgenstein’s distinctive approach to number systems whether elementary or transfinite. Examples are presented to illuminate the relation between the meaning of an arithmetical generalisation or theorem (...) and its proof. An attempt is made to meet directly some of Wittgenstein’s critical comments on the mathematical treatment of infinity and irrational numbers. (shrink)

Along with “paradigm” and “scientific revolution,” “incommensurability” is one of the three most influential expressions associated with the “new philosophy of science” first articulated in the early 1960s by Thomas Kuhn and Paul Feyerabend (see kuhn and feyerabend). But, despite the fact that it has been widely discussed, opinions still differ widely as to the content and significance of the claim of incommensurability. What is uncontroversial is that the term “incommensurability” was borrowed from mathematics, where it can be used, for (...) example, to apply to the relation between the side of a square and its diagonal. Since the side of a square is measured by a rational number, and its diagonal by an irrational number, and since an irrational number cannot be represented by a point on the rational number line, the two quantities are said to have no common measure; they are literally incommensurable. Kuhn and Feyerabend adapted this term and applied it to some pairs of rival scientific theories, to indicate that such theories also had no common measure, or, in some sense to be determined, could not be compared directly. Both Kuhn and Feyerabend agree that they hit upon the term independently and used it in print for the first time in 1962, in The Structure of Scientific Revolutions and “Explanation, reduction, and empiricism,” respectively. But the two writers explicate the claim and argue for it rather differently. After tackling the concept of incommensurability as it appears in the works of each of these authors in turn, some reactions and responses will be sampled. (shrink)

In this chapter, we will provide an overview of Richard Dedekind's work on continuity, both foundational and mathematical. His seminal contribution to the foundations of analysis is the well-known 1872 booklet Stetigkeit und irrationale Zahlen (Continuity and irrational numbers), which is based on Dedekind's insight into the essence of continuity that he arrived at in the fall of 1858. After analysing the intuitive understanding of the continuity of the geometric line, Dedekind characterized the property of continuity for the (...) real numbers in terms of what are nowadays called 'Dedekind cuts' on the rational numbers. This treatment, which can be characterized as being 'arithmetical' as well as 'axiomatic', will be presented in detail. To better position Dedekind's contributions in their historical context, we will also consider some of his more mathematical treatments of continuity in addition to his foundational work. Of particular interest is the definition of the Riemann surface in his joint work with Heinrich Weber (1882). Moreover, Dedekind's reflections on space and continuity in his unpublished papers 'Allgemeine Sätze über Räume' (General theorems about spaces; before 1870) and 'Beweis und Anwendungen eines allgemeinen Satzes über mehrfach ausgedehnte stetige Gebiete' (Proof and applications of a general theorem about multiply extended continuous domains; 1892) illustrate the wide range and general coherency of his thoughts. By discussing Dedekind's works in which the notion of continuity plays a central role, we will show how Dedekind's approaches became increasingly abstract, while at the same time retaining a common methodology. (shrink)

This Element aims to present an outline of mathematics and its history, with particular emphasis on events that shook up its philosophy. It ranges from the discovery of irrational numbers in ancient Greece to the nineteenth- and twentieth-century discoveries on the nature of infinity and proof. Recurring themes are intuition and logic, meaning and existence, and the discrete and the continuous. These themes have evolved under the influence of new mathematical discoveries and the story of their evolution is, (...) to a large extent, the story of philosophy of mathematics. (shrink)

All through the XXth century it has been repeated that "there is an exact correspondence, almost coincidence between Euclid's definition of equal ratios and the modern theory of irrational numbers due to Dedekind". Since the idea was presented as early as in 1908 in Thomas Heath's translation of Euclid's Elements as a comment to Book V, def. 5, we call it in the paper Heath's thesis. Heath's thesis finds different justifications so it is accepted yet in different versions. (...) In the paper its historical and mathematical version is reconstructed. We next reconstruct Eudoxos' theory of proportions in an axiomatic fashion. Finally, we show that Heath's thesis both in the historical and mathematical version is false. To this end a counterexample is given; it is based upon a specific interpretation of the uniform distribution theorem. (shrink)

This paper presents the first edition, translation and analyse of al-Mns commentary of the Book X of Euclid one. For the first time, irrational numbers are defined and classified. The algebraisation of Elementsrizms Algebra, shows irrational numbers as solution to algebraic quadratic equations. The algebraic calculus makes here the first steps. On this occasion, negative numbers and their calculation rules appears. Simplifications imposed by the algebraic writings are sometimes in opposition with the conclusions of propositions (...) conceived in a purely geometrical framework, revealing a contradiction between geometrical and algebraic goals. It will be resolved by the independant way algebra will take with mathematicians belonging to the tradition of al-Karajal from the 11th-12th centuries on. (shrink)

The fine structure constant appears in several fields of physics and its value is experimentally obtained with a high accuracy. Its physical origin however is unsolved long-standing problem. Richard Feynman expressed the idea that it could be similar to the natural irrational numbers, pi, and e. Amongst the proposed theoretical expressions with values closer to the experimental one is the formula of I. Gorelik which is based on rotating dipole with two empirically suggested coefficients, while the physical origin (...) is unknown. BSM-Supergravitation Unified Theory suggests a physical mechanism defining the fine structure constant. The mathematical expression is based on a spatial precession mode of vibrations in a tetrahedron of spheres with specific properties. The value from the derived expression differs from the CODATA 98 value by 0.000008% only. The conclusion is that the fine structure constant is a natural irrational number. While the irrational number pi, is defined in a 2D space, the fine structure constant is related to a vibration property of a specific formation in 3D space. (shrink)

In recent years the magnificent world of fractals has been revealed. Some of the fractal images resemble natural forms so closely that Benoit Mandelbrot's hypothesis, that the fractal geometry is the geometry of natural objects, has been accepted by scientists and non-scientists alike. The present paper critically examines Mandelbrot's hypothesis. It first analyzes the concept of a fractal. The analysis reveals that fractals are endless geometrical processes, and not geometrical forms. A comparison between fractals and irrational numbers shows (...) that the former are ontologically and epistemologically even more problematic than the latter. Therefore, it is argued, a proper understanding of the concept of fractal is inconsistent with ascribing a fractal structure to natural objects. Moreover, it is shown that, empirically, the so-called fractal images disconfirm Mandelbrot's hypothesis. It is conceded that the fractal geometry can be used as a useful rough approximation, but this fact has no bearing on the physical theory of natural forms. (shrink)

The derivative is a basic concept of differential calculus. However, if we calculate the derivative as change in distance over change in time, the result at any instant is 0/0, which seems meaningless. Hence, Newton and Leibniz used the limit to determine the derivative. Their method is valid in practice, but it is not easy to intuitively accept. Thus, this article describes the novel method of differential calculus based on the double contradiction, which is easier to accept intuitively. Next, the (...) geometrical meaning of the double contradiction is considered as follows. A tangent at a point on a convex curve is iterated. Then, the slope of the tangent at the point is sandwiched by two kinds of lines. The first kind of line crosses the curve at the original point and a point to the right of it. The second kind of line crosses the curve at the original point and a point to the left of it. Then, the double contradiction can be applied, and the slope of the tangent is determined as a single value. Finally, the meaning of this method for the foundation of mathematics is considered. We reflect on Dehaene’s notion that the foundation of mathematics is based on the intuitions, which evolve independently. Hence, there may be gaps between intuitions. In fact, the Ancient Greeks identified inconsistency between arithmetic and geometry. However, Eudoxus developed the theory of proportion, which is equivalent to the Dedekind Cut. This allows the iteration of an irrational number by rational numbers as precisely as desired. Simultaneously, we can define the irrational number by the double contradiction, although its existence is not guaranteed. Further, an area of a curved figure is iterated and defined by rectilinear figures using the double contradiction. (shrink)

An overview of the history of the concept of matter highlights the fact that alternative modes of explanation were successively employed. With the discovery of irrational numbers the initial conviction of the Pythagorean School collapsed and was replaced by an exploration of space as a principle of understanding. This legacy dominated the medieval period and had an after-effect well into modernity—for both Descartes and Kant still characterized matter in spatial terms. However, even before Galileo the mechanistic world view (...) slowly entered the scene—the world as chaos, particles in motion. Elevating movement to become the guiding principle in our understanding of matter dominated the main tendency of modern physics until the (end of the) 19th century. The discovery of irreversible processes (radio-activity for example) directed 20th century physics towards an exploration of the meaning of energy-operation. It turned out that even within 20th century physics long-standing legacies prevailed, because an account of the nature of matter continued to be torn apart by atomistic and holistic views—confronted by the problem of constancy and change (radical transformability versus persistence). Concrete, material reality exceeds the scope of any single mode of explanation—an insight that also serves a better understanding of the wave-particle duality. (shrink)

This book investigates the relation between mathematics and philosophy in Kant with special focus on the doctrine of the magnitudes. Without doubt, Moretto, who is himself both a mathematician and a philosopher, achieves final results on this matter, because not only does he provide an immanent interpretation of all parts of Kant’s systematic construction of magnitudes, he also provides a detailed history of Kant’s development. Kant gave courses on mathematics during the first eight years of his teaching at Königsberg and (...) warmly recommended the study of mathematics to his most gifted disciples. He himself expressed a profound admiration for it. He wrote in The Only Possible Argument in Support of a Demonstration of the Existence of God that infinitesimal analysis, or, as he calls it, “higher geometry... in its account of the affinities between various species of curved lines,” reveals many of “the harmonious relations which inhere in the properties of space in general.... All these relations, in addition to exercising the understanding by means of our intellectual comprehension of them, also arouse the emotions, and they do in a manner similar to or even more sublime than that the contingent beauties of nature stir our feelings”. In On the Form and Principles of the Sensible and Intelligible World, Kant wrote that pure mathematics “provides us with a cognition which is in the highest degree true, and, at the same time, it provides us with a paradigm of the highest kind of evidence in other cases”. Besides, the mathematician-philosophers of the Leibniz-Wolff school, J. A. Eberhard, J. C. Schwab, J. G. E. Maaß at Halle, and A. G. Kästner at Göttingen, were among the very first to move critiques against the Critique of Pure Reason by focusing on the problem of the foundation of mathematics. They defended Leibniz against Kant, which prompted Kant to start a mathematical school of his own at Königsberg, and J. Schultz, J. G. K. C. Kiesewetter, and C. G. Zimmermann were Kant’s most notable defenders. Finally, one should not forget that it was in order to introduce a completely new set of ideas concerning the philosophy of mathematics that Kant laid out not only the distinction between analytical and synthetical judgments, but also the whole of the transcendental aesthetics. In fact, Kant proposed giving foundation to rational absolute numbers by means of synthetical a priori judgments; he also considered all arithmetical judgments as synthetical a priori; and by dedicating two antinomies to infinite series he suggested analogies to the representation of infinite series of irrational numbers. (shrink)

This paper attempts to demonstrate that the conviction about the harmony and order of the world was a fundamental metaphysical principle of the Pythagoreans. This harmony and order were primarily sought in the structures of arithmetics, yet following the discovery of incommensurable magnitudes (irrational numbers, as we now call them), the Pythagoreans began to see geometrical structure as a fundamental part of the world. On the example of the Pythagoreans’ metaphysics and science, the paper shows the mutual relations (...) between metaphysics and science. It demonstrates— on the one hand—the necessity of the first as a guide for the latter, and—on the other—how our scientific research can change its basic metaphysical principles when these are found to be inappropriate. The paper also tries to show the need for a realistic approach in our scientific research by means of the same example of the Pythagoreans, that is, the need to discern something which is below the surface appearance. (shrink)

We give a polynomial time controlled version of a theorem of M. Hall: every real number can be written as the sum of two irrational numbers whose developments into a continued fraction contain only 1, 2, 3 or 4.

Pattern recognition is represented as the limit, to which an infinite Turing process converges. A Turing machine, in which the bits are substituted with qubits, is introduced. That quantum Turing machine can recognize two complementary patterns in any data. That ability of universal pattern recognition is interpreted as an intellect featuring any quantum computer. The property is valid only within a quantum computer: To utilize it, the observer should be sited inside it. Being outside it, the observer would obtain quite (...) different result depending on the degree of the entanglement of the quantum computer and observer. All extraordinary properties of a quantum computer are due to involving a converging infinite computational process contenting necessarily both a continuous advancing calculation and a leap to the limit. Three types of quantum computation can be distinguished according to whether the series is a finite one, an infinite rational or irrational number. (shrink)